【正文】 more liabilities, the greater the value of the pany. Corporate debt as a result of the interest can be taxfree, which the pany has provided the stimulus to use more debt, as the present value of taxfree to increase the pany39。s market value, the goal will be to maximize the value of the pany to take all the debt capital structure, capital structure that is best for 100% of the debt. The actual situation in general does not support this conclusion, so the vast majority of people think that there are other market imperfections, and That is a result of overborrowing and the financial deficit caused by the insolvency probability and the risk of depression than the pany39。s debt. This is logical, but its price is to changes in corporate finance debt into the tax benefits and bankruptcy cost tradeoff studies.(2) The existence of the personal ine tax under the conditions of the MM theorem. Miller pointed out that before 1986 in accordance with . tax law, individuals from the bonds and stocks have to pay ine tax rate is different. In terms of the interest ine, dividend ine and interest ine should be included in debt personal ine tax paid by the class. But the stock returns of capital gains (stock price) the effective tax rate lower than the stock and bond interest ine tax, capital gains because the stock in the first 60% of the longterm capital gains are taxfree, and only in the practical realization of capital gains, that is, sell shares after the payment of tax, of unrealized potential capital gains are taxfree. Therefore, on average, the Shares of tax revenue to be less than the proceeds of tax bonds. This obviously will affect the individual39。s investment decisions.Although the increase in borrowing limit in order to find a tendency to brake and the introduction of a progressive personal ine tax, but we are from Miller, the model itself, it also called for in order to maximize the value of the pany, the pany should have 100% of the liabilities and equity liabilities are position. However, logically, 100% of the liabilities of the shareholders does not exist, and in fact bee a creditor of the business owners. Reality shows that no pany is 100% liability, so the scholars of the MM theory and the theory of eating Miller considerable skepticism. Is generally believed that these theories of the derivation itself is not wrong, the problem from the theoretical most aggressive of a theoretical argument is that MM does not take bankruptcy costs and agency costs.2. The Tradeoff theoryTradeoff theory is used in reference to Myers, but this formulation is not appropriate, because the broad sense, the history of the way of capital structure theory is a tradeoff theory of history, the main elements are the costs of capital structure research weigh the issues and interests. So not used to weigh a specific school, we have to weigh the meaning of this is theoretical orientation: the 20th century, the mid70s to form the academic theory of capital structure on the general point of view, the view is that the optimal capital structure of enterprises in the tax benefits and liabilities of bankruptcy cost tradeoff between the present value. So tradeoff theory can also be known as the theory of optimal capital structure.After the development of tradeoff theory for the posttradeoff theory, the theory of the cost of the liabilities from the further expansion of bankruptcy costs to the agency costs, financial distress costs and nontax loss of interest, etc. At the same time, then the tax benefits extended to the interests of nontax liabilities In fact, is the expansion of the costs and benefits of what is contained in the optimal capital structure of panies as a tax benefit in a variety of cost and liabilities related to the balance between the cost.3. The introduction of asymmetric information theory of the new capital structureNew capital structure theory to a focus only on antitax, bankruptcy and other external factors for most enterprises the impact of capital structure theory, trying to asymmetric information theory of the signal, motivation, incentives such as the concept of from the enterprise of internal factors to start on the issue of capital structure analysis. So as to balance the capital structure problem into a structure or system design problems, thus the capital structure to the theoretical issues opened up new research directions, provide a new interpretation, so that the capital structure theory since then have entered a new stage of development, we call The theory of capital structure for the new.New theory of capital structure is characterized by one of the largest recognized the asymmetry of information in the capital structure decision in the role, Meyers, and theoretical perspectives Meki Sharif：In the study the role of agency costs and capital structure to the Department of Asymmetric Information regard, Myers has been the most influential one of the scholars. Meyers and Meki Sharif pointed out that if investors do not like people do party vendors and internal value of the assets of the manufacturers of the wellinformed information, then the equity market may be priced incorrectly. If panies need to issue stock to finance new projects, if the stock price is too low as a result of new investors to the extent that the new project than NPV (net present value that is) more of the value of existing shareholders will result in a net loss of . In this case, even if NPV is positive, the project will be rejected. If manufacturers can take advantage of its market value so do not underestimate the securities financing for new projects，Lack of such investment will be avoided. Therefore, in this case, with more preference shares pared to firms inhouse funds, and even the risk of not too much debt than equity superior. Because of this, Myers pointed out that the capital structure for the new panies will be subject to the wishes of the financing of investmentdriven, f