Abstract: The composite coatings of Fe-Ni-Cr-La2O3 is applied on the surface of 45 steel substrate by means of medium and high frequency induction heating, and OM, SEM, EDS, micro-hardness tester and Rockwell hardness tester were used to study the effect of La2O3 addition amount on the microstructure, element distribution, surface hardness and section micro-hardness of the composite coatings, objective to find out the optimal amount of La2O3 added to the coatings prepared by this method. The results show that the addition of La2O3 can improve the mutual diffusion between the elements in the coatings and between the coatings and the matrix, and improve the surface hardness and section micro-hardness of the coating. However, more La2O3 is added is not necessarily better, there is an optimal La2O3 addition amount. When the La2O3 addition amount is 2%, the internal defects of the Fe-Ni-Cr-La2O3 composite coatings are the smallest, the mutual diffusion between the elements in the coating and the matrix is obvious, the dendrite structure at the joint is refined, the intra-crystalline and grain boundary component segregation of the coating is the smallest, the surface hardness of the coating is increased by 7.2% compared with the coatings without La2O3 addition amount, and the longitudinal section micro-hardness of the coatings is the highest, which is the optimal addition amount of La2O3 in the composite coatings.