Fluid-solid coupling numerical simulation on the flow and heat transfer of cooling water-jacket in cylinder head for 226B diesel engine was performed using the commercial CFD software STARCD and the FEA software ABAQUS. In order to consider the influence of boiling heat transfer, a boiling heat transfer model was developed based on FORTRAN and built into STAR-CD. Comparison between simulation and experiment showed that the two results are in good agreement with each other. Comparing with the results of simulation without the boiling heat transfer model, maximum deviation drops from 18% to 7%. So the simulation provides a more dependable theoretical evidence for diesel water-jacket optimization.