According to the relationship between the load and the relative axial deformation value of the diaphragm spring, six important characteristic parameters are analyzed by using MATLAB, including the height of the internal truncated cone of the disc spring in the free state, thickness of steel plate, radiuses of large and small end of disc spring part without any force, the radius of pressure plate loading point and loading point of support ring. The influences of characteristic parameters on the performance of diaphragm spring are summarized. The optimization of a diaphragm spring improves the performance of the clutch and prolongs the abrasion limit of the clutch.