Abstract: Ownership structure is the basis of corporate governance, so different ownership structure affects investment behavior and even the value of company. However, no ownership structure is perfect.it is out of consideration of its advantages and disadvantages that the domestic capital market has gradually begun to accept dual-class share structures companies. Therefore, the further study and discussion of these companies meet the needs of domestic capital market practice. The paper compares and analyses the difference of investment efficiency between dual-class share structure companies and the single ones which were listed in U.S. based on the samples of them from 2008 to 2017, and the difference of managerial shareholding ratio of two types of companies on inefficient investment. Research shows both types of companies have problem of non-efficiency investment, and the dual -class share structures companies show the behavior of overinvestment compared with the single one; by examining the impact of managerial shareholding on investment in two types of companies, it finds compared with single-class share structure companies, improving the cash flow rights of management shareholders would contribute more to restrain the non-efficiency investment(overinvestment) in dual-class share structures companies, as the extent of voting rights and separation increasing, the non-efficiency investment(overinvestment) would be promoted more, and the greater the degree of separation of ownership and control, the more serious the inefficient investment behavior is; the same result is also shown for the samples of overinvestment, that is, the promotion effect of management voting rights on overinvestment, the restraint effect of cash flow rights and the degree of separation of the two rights on overinvestment are more obvious than that of single ownership structure company. This study has a unique perspective, novel samples and intuitive process, hoping to provide useful reference for further discussion of the problem and corporate governance, market supervision.

Key words: dual-class share structures, overinvestment, underinvestment, separation of ownership and control