Composite drillbit spherical sliding bearing is a new structure of bit bearing. There is no related literature to make thorough study of its mechanical behavior. Therefore,the ANSYS finite element analysis was adopted to establish the spherical composite bearing three-dimensional model; Used the contact finite element calculation to comparison and analysis the surface pressure distribution size and regularity of spherical and cylindrical; Lastly,used the spherical radius as design variables and the peak contact pressure as objective function establish composite bit sliding bearing optimization design model. The optimization results show that: the peak contact pressure decreased 50. 6%. The peak stress of von Mises decreased 17. 7%. The contact pressure distribution is more reasonable. The new structure can effectively improve the sliding bearing service life and working reliability.