Abstract: The paper takes 961 corporations listed on China's stock market from 2014-2016 as empirical research data. It deduced the role of Agency cost between ultimate control and corporate performance reversely. It revealed the operation mechanism inside the "black box" to some extent, by analyzing different paths of two types of agency costs between ultimate control and corporate performance. Empirical results are as follows:the nature of ultimate control rights negatively moderated the positive correlation between the concentration on ultimate control and corporate performance. The agency costs mediated the positive correlation between the concentration on ultimate control and corporate performance. Ultimate control moderated the mediating effects of agency costs between ultimate control and corporate performance. The private ultimate control rights reduced the agency cost from the first type of agency cost. But it increased the second type of agency cost. The state ultimate control concentration inhibited the second agency cost, but will increase the first agency costs.