Abstract: Studies the effect upon piston temperature field from changes in positions of the cooling gallery.A FEM piston model for a model 1015 engine was developed on Pro/E and thermal simulations achieved through ANSYS. Rigorous simulations were performed to find the temperature change rules and the sensitivity of piston temperature field with regard to the cooling gallery position. The results demonstrated that the position of cooling gallery has various effects upon the piston temperature. The temperature of top-ring groove can be reduced by 30 degree centigrade by moving the cooling gallery upward. The velocity of temperature change in the top-ring groove attained a global maximum.