In order to investigate the thermal load distribution of modified piston, it is necessary to analyze temperature field and thermal stress combined simulation with experiments. The FE software was used to simulate the temperature field of the piston after the boundary conditions of thermal transfer were calculated, and then, the results were verified according to experiment data, and the error of calculation was less than 5%. Finally, temperature field and thermal stress were derived under different operating conditions including conditions A and B. The results of investigation show that the maximum temperature and maximum value of thermal stress of modified piston decrease compared with the original piston. The modified piston meets the demand of thermal load based on the original piston meeting the demand of thermal load.