Ni-P-Al2O3 composite coatings with the uniform distribution of Al2O3 particles were prepared by adding Al2O3 particles into Ni-P plating solution and adopting optimum plating process. The morphology and microstructure of the coatings were investigated by using SEM, EDS and XRD. Being immersed in 10 vol.% H2SO4 solutions, the corrosion resistance of Ni-P-Al2O3 composite coatings was tested. The results show that when the solubility of Al2O3 particles in plating solution is 8 g/l, the corrosion resistance is best. Comparing with as-plated Ni-P-Al2O3 composite coatings, the corrosion resistance of heat-treated Ni-P-Al2O3 composite coatings decreases by raising the temperature to 300°C and then increases by raising the temperature to 450°C.