Abstract: The ways of four-point bend test and acoustic emission were used, the failure pattern(cohesive failure,coating debonding) of Ni-P electroless plating and composite plating that varied with the heat treatment temperature were obtained. The results showed that the rear earth's balance deviation between coating and interface of substrate and particles was able to improve the strength of interface,crackle load,crackle deviation and extend strength of crackle. The heat treatment above 400℃ greatly improved adhesive strength between plating and substrate material, thus making coating change from interface crackle to cohesive crackle.