To study the influence law of piston pinhole profile and inner diameter on pinhole fatigue strength, a finite element simulation model of piston and components was established. The optimal matching scheme of pinhole profile and piston pin, verified by engine bench test, was obtained by simulating and calculating how different pinhole profiles and piston pin inner diameter can affect the pinhole pressure and fatigue strength. The results show that the pinhole profiles do have greater influence on the contact pressure and fatigue strength in the pinhole; The piston pin inner diameter mainly affects fatigue strength of pinhole and pin, as well as elliptical deformation of piston pin rather than the contact pressure of piston pin. For every 1 mm increase in the inner diameter of piston pin, the fatigue coefficient of pinhole will decrease by 6.2%~11.2%, the elliptical transformation of piston pin will increase by 10%~15%, and the fatigue coefficient of piston pin will decrease by 3.2%~9.8%. Therefore, it can improve the fatigue strength of pinholes and reduce the risk of pin hole cracking and failure effectively by adjusting the hyperboloidal shrinkage of pinhole profile and decreasing the piston pin inner diameter, which provides theoretical and engineering application references for improving the reliability of internal combustion engine pistons.