The invention discloses a method for checking the piston strength of an engine, which belongs to the piston field of the engine and comprises the following steps: a finite element mesh partition is performed on a piston, a piston pin, a connecting bar and a cylinder sleeve; a loading heat-transferring boundary condition is performed on the piston, the piston pin, the connecting bar and the cylinder sleeve which are processed through the finite element mesh partition; solution is performed on a piston temperature field, and then the calculations on heat stress, mechanical stress and fatigue are performed; the result evaluation is performed on the piston which is processed through the solution of the temperature field and the calculations on the heat stress, the mechanical stress and the fatigue. Through the technical proposal of the method, the product development period is shortened greatly, various performances of the piston under actual working conditions can be simulated in a theoretical environment before a sample piece is trial-produced, the development efficiency is increased, the experimentation cost is saved greatly, and the design direction of the piston products is shown clearly.