Piston is one of the key components in a motor and it closely relates to the machine performance, carbon emissions and the economy. With the engine higher speed and strengthen developing, its higher pressure ratio and higher power improve constantly. Pistons work condition is more and more bad, so its reliability has become the key factors to improve engine reliability. Structure and working environment of pistons are very complex. In the working environment, the pistons will produce stress and deformation because of the periodic load effect, which are from high gas pressure, high speed reciprocating motion from the inertia force, lateral pressure, friction and so on. Burning of the high pressure gas products high temperature, which makes piston expands in order that its interior produces thermal stress and thermal deformation. The thermal deformation and mechanical deformation will cause piston cracks, tortuosity, etc. Therefore, it is essential to analytic the stress field, temperature field, heat transfer, thermal load and mechanical load coupling of piston in order to lower the heat load and improve the thermal stress distribution and improve its working reliability during the piston designed. Analysis method of the finite element provides a powerful calculation tool, which is better than test method and theory analysis method and has become an important means for internal combustion engine performance study.