Abstract: Aiming to solve the leakage problem of cylinder head, the effect of thermal annealing process, machine manufacturing process and testing process on residual stress of the cylinder head was analyzed by using blind-hole method. The results show that the thermal annealing process, which was with higher holding temperature, longer holding time, lower cooling rate and lower out-of-furnace temperature, was able to keep lower residual stress of the rough cylinder head. The residual stress of the cylinder head was increased after machine manufacturing process. Through the optimization of thermal annealing process, residual stress of bottom surface of the cylinder head was effectively controlled. No crack was found after 1 000 h bench testing, indicating that the optimization of thermal annealing process can greatly reduce the residual stress of bottom surface of the cylinder head and effectively solve the leakage problem of the cylinder head.