Objective To improve the tribological properties of NiCoCrAlY/ Al2O composite coating. Methods The NiCoCrAlY/ Al2O3 and NiCoCrAlY/ B4C composite powders were prepared by the technology of spray granulation, chemical and metallurgical coating and solid state alloying. The NiCoCrAlY / Al2 O3 -B4 C composite coatings were prepared by atmospheric plasma-spray tech- nology. The microstructure, tensile strength and microhardness were studied in order to investigate the effect of B4 C content on the mechanical properties of atmospheric plasma-sprayed NiCoCrAlY / Al2 O3 -B4 C composite coatings. Results The Al2 O3 and B4 C were coated by NiCoCrAlY alloy, respectively, and the thickness of NiCoCrAlY alloy was 3 ~ 5 μm. The composite coatings consisted of elongated lamellae and they integrated with each other very well. The microhardness of the coatings increased and the tensile strength of the coatings decreased with the increasing B4 C content. The microhardness of the coatings was 1. 4 times higher than that of the coatings without B4 C and the tensile strength of the coatings decreased by 26% as compared with that of the coatings without B4 C, when the B4C content was 30% . Typical brittle fracture occurred in the coatings in the tensile test and the fracture locations were inside the coatings. Conclusion The addition of B4 C into the atmospheric plasma-sprayed NiCoCrAlY / Al2 O3 could improve the microhardness of the coatings, but it also destroyed the tensile strength of the coatings.