Abstract: To solve the failure problems of diesel engine ductile iron pistons caused by the high temperature, high pressure and periodic thermal−mechanical loads during operation, a method combining experimental testing and numerical simulation was adopted to conduct temperature field tests and material creep−fatigue life tests on the ductile iron piston, with a certain diesel engine ductile iron piston taken as the object. A heat transfer numerical model for the ductile iron piston was established and calibrated. The temperature field, thermal stress and thermal−mechanical coupling stress of the piston under the rated condition and the maximum torque condition were analyzed. The lifespan of the ductile iron piston under creep−fatigue damage was evaluated. The results show that the maximum creep−fatigue damage of the ductile iron piston under cyclic loads of rated conditions and maximum torque conditions is 0.21, and the creep−fatigue life is 1 064 times, and failure position is located in the combustion chamber cavity of the piston.