Residual stress and microcracks inevitably exist in plasma spraying coatings. In order to reduce the residual stress of the TiN coating prepared by reactive spraying, Ni/G was added to the TiN coating. TiN-Ni/G composite coatings were prepared on the surface of 45# steel. The effects of Ni/G content on the microstructure, microhardness and erosion resistance of the coating were studied, and the erosion mechanism of coatings in slurries with different pH values was analyzed. The results showed that the average hardness of the TiN-Ni/G composite coating was about 1000HV0.2, and coatings were impacted by SiO2 particles and corroded by the solution during the erosion process of the coating in 5wt.%NaCl slurry; the coating was mainly subjected to the impact of SiO2 during the erosion process in the NaOH mud at pH=10, and the mass loss of the coating in NaOH mud was significantly reduced compared with that in the neutral solution. When the Ni/G content is 11wt.%, the coatings show good impact resistance.