The work aims to discuss crack initiation characteristics and life evaluation method of diesel engine Si-Al alloy block in fretting state in respect of fretting fatigue failure phenomenon between diesel engine block and fastening surface of main bearing cap. The finite element model of the block fastening surface composite structure was built, and stress/strain historical data on fastening surface of the block was analyzed. On this basis, contact state of the fastening surface on the block was analyzed, and influences of friction coefficient and friction work on the fretting fatigue characteristics were discussed. Multi-axis fatigue parameters, CCB, F, SSI and Ruiz, were used to predict crack initiation position of the block. The model was built for predicting the fretting fatigue life of the block by modifying all parameters. Compared with the experimental values, the F and SSI parameters in prediction results differed greatly from those in experimental results. The life prediction results of CCB and Ruiz parameters were close to the experimental values, and fall within a scatter band of 2.3. However, the crack initiation position predicted with CCB parameter was inconsistent with actual fracture position of the block, hence the parameter could not be used to predict fretting fatigue life of the block. Microcracks may easily appear in the contact region subject to sudden change, and fretting fatigue damage can be suppressed by appropriately increasing friction coefficient or decreasing friction work. Fatigue life of the block predicted with Ruiz parameter is in a good accordance with the experimental values. It is feasible to evaluate the fretting fatigue of diesel engine by using Ruiz parameter within a scatter band of 2.3.