Abstract: By means of fatigue test,the S-N curves of new and used engine cylinder heads were compared. It was found that the fatigue lives had an obvious contrast between new and used materials in the case of a large stress amplitude,while in a small stress amplitude,the difference between them was very little. It can be concluded that the damage degree of engine cylinder head after refabrication will become serious along with the increase of stress amplitude. In a word,as the result of damage accumulation,the engine may have a hidden trouble of safety after refabrication.