11%～46%。3-D finite element models and meshes of the cylinder in a certain vehicle diesel engine were established. With the combination of finite element analysis and submodel technology, ABAQUS software was used to carry out finite element strength analysis on engine block. Then the stress concentration position was determined and structural improvement of cylinder block was proposed. Based on this, MSC.Fatigue software was adopted to calculate fatigue strength of the water jacket basement submodel before and after modification, and stress test was done to validate the effect. The experiment results indicated that the stress of water jacket basement reduces from 11% to 46% after adding stiffening rib to the cylinder.