Anchorage zone on tower of cable stayed bridge has complex structures and stress distributions, and keeping it on a safety state under a large tonnage tension and prestress is more concerned in design and construction. The stress distribution of the anchorage zone was analyzed by 3D finite element method. Furthermore, the mechanical properties and the rules of stress distributions were investigated and compared in three different load cases. The results show that the disposition form of level prestressing tendon is reasonable. The stress of the entire tendon is very close to 1 116 MPa under the tension control stress of 1 260 MPa. It is shown that the intensity of the tendon has given full play to prestress and it is not appropriate to increase the tension control stress.