Abstract: The inner surface spalling phenomenon of connecting rod bushing of a piston engine occurred many times. The causes of inner surface spalling of bushing were analyzed by means of macroscopic observation, scanning electron microscope and energy spectrum analysis, metallographic examination and simulation test. The results show that there were abnormal microstructures such as interdendritic pores and disappearance of lead particles on the near surface of the copper alloy lining, resulting in insufficient local bearing capacity. The reason for the abnormal microstructure near the surface of the copper alloy lining was that the acid solution was used to remove the lead-tin alloy coating for too long during the overhaul, and the interdendritic lead particles of the copper alloy layer were seriously dissolved by the acid solution.