Periodically, engine block-bearing cap structure is subject to the mixed bearing load from combustion and inertia mass of crank. Recently, due to the trend of lightness, cast steel is replaced with aluminum in the material of gasoline engine block. And, the load acting on the main bearing cap is rapidly rising due to the increase of engine power. Therefore, in the development stage, fretting fatigue failures frequently occurred on the block face contacted with the bearing cap. Fretting is a kind of wear which is occurred by micro relative movement. Even though various researches have been made to investigate fretting fatigue failure with FEA approaches, they are not enough to evaluate the phenomenon. In this study, the new CAE method simulating the fretting fatigue failure on the engine block face is developed and the mechanism of the fretting fatigue on the engine block is investigated. As the results, the FS parameter showed a good correlation with the fretting fatigue crack position and a good agreement between numerical and experimental results.