Based on conjugate heat transfer method, the influence of coolant flow on temperature distribution of cylinder block-cooling water coupling model and thermal deformation of the cylinder liners were calculated on the results of CFD analysis for the whole cooling water system by using commercial software ANSYS. The flow and pressure filed of the whole cooling system, the temperature distribution of the coupling model and thermal deformation of the cylinder liners were demonstrated, which showed that the temperature and thermal deformation had remarkable changes along axial and circumferential direction, and these also provided theoretical evidence for failure simulation and optimization design of diesel engine.