Abstract: The bolt-ball joint system widely used in china is a typical semi-rigid joint. Based on the mechanical characters of bolt-ball joint system, three-dimensional solid models of three bolt-ball joints are established through software ANSYS using solid elements and contact elements. With the geometric and material nonlinearities taken into consideration, the bending stiffness of bolt-ball joint is analyzed and the moment-rotation curves are obtained. Experimental study is also carried out to obtain the moment-rotation curves of the bolt-ball joint to verify the numerical simulation results. The experimental results agree well with the theoretical ones, indicating that the numerical simulation is accurate and effective to simulate the bolt-ball’s mechanical characters. This numerical simulation results can serve as technical reference for design and application of the bolt-ball joint and other semi-rigid joints.