Equity ownership convergence has an incentive force for the controlling shareholder to exploit rents, which has damage to the firms. Suppose rents the controlling shareholder exploits from the corporation are equal and fixed every period on the environment Of law, system and administration. A model is built which integrates the controlling shareholder benefit and his exploiting rents. The interesting results are found as follows. In general the controlling shareholder exploits rents if he estimates the firm lifetime below the critical point of time. The speed of firm development, share proportion by the controlling shareholder and firm earning affect the critical point of time. Price premium in big block trade of shares can nearly measure value of rents the controlling shareholder exploits; present value of rents is above price premium by tender offers in capital market, and it is equal to price premium by negotiated block. The results tell us that improving expected firm lifetime may diminish the controlling shareholder exploiting rents.
