Abstract: To study the influence of forced cooling on the secondary motion and force of piston, this research measured discrete temperature on the surface of the piston by hardness bolt, simulated temperature and deformation field with finite element method software, and analyzed the secondary motion and force in different deformation through multi-body dynamics method. The results show that：The temperature and deformation with forced cooling differ from the original one with decreased temperature and deformation range. Due to those changes, the max amplitudes of the piston’s lateral motion and swing around the pin increase with 25% and 27.8% respectively, while the force acted on the piston increase by 36.8% which results in the abrasion deterioration on the piston shirt.

Key words: forced cooling, heart deformation field, heart deformation field, profile of piston