The temperature and thermal stress distributions of ceramics/metal functional gradient cylinder were simulated by finite element method (FEM). Using the indirect solution method of thermal analysis and subsequently structural analysis of ANSYS10.0 software, the simulations were carried out under stable working conditions and the third type boundary conditions of piston in IC engine. The effects of gradient composition distribution index p on the temperature of piston head and the thermal stress at the gradient layers of ceramics/metal were studied respectively. Finally, the optimal design result corresponding to the gradient composition distribution index p=0.6 was obtained for easing the thermal stress.