The share ownership structure of commercial banks, which is an important aspect of commercial banks' governance, directly influences commercial banks' agency costs. According to the analysis of various documents, this artical finalize the conclusions, including what the major factors of commercial banks' agency costs are, offering their corresponding hypothesis and through data model, observing how the share ownership structure affects the agency costs. Studies show that through share ownership's balance degree, banks can effctively reduce the agency costs; Banks, whose high proportion shareholder is the nation, can decrease the rate of the national shareholding to cut the agency costs; On the other side, reducing capital adequacy ratio cannot decrease the agency costs. Similarly,when discussing the concentration ration affects the agency costs, the same problems raise.