Abstract: Taking the cylinder head of a six-cylinder diesel engine as the research object, the boundary conditions of temperature field analysis were determined by CFD calculation and empirical formula, and then the temperature field analysis was carried out.The coupling stress field of the cylinder head under thermal load and mechanical load is analyzed, and the dangerous points on the cylinder head are determined.When calculating the stress field of the cylinder head, the plastic strain of the material and the unbalance of each cylinder are considered, and the high cycle fatigue safety factor and low cycle fatigue life of the cylinder head are calculated.The results show that the life of some areas of the cylinder head is low, and these areas need to be optimized.