Abstract Conventional, submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel (HVOF). The microhardness and microstructure of the coatings were compared, and the resistance of the coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment. Cavitation pits and craters were observed by SEM and cavitation mechanisms were explored. The results show that the microstructures of submicron and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity, and their microhardness values are obviously higher than that of the conventional WC-12Co coating. The average microhardness of multimodal WC-12Co coating reaches nearly HV1500, which is much higher than that of the conventional one. As well, it is found that the multimodal WC-12Co coating exhibits the best cavitation erosion resistance among the three coatings, the erosion rate is approximately 40% that of the conventional coating, and the cavitation erosion resistance of multimodal WC-12Co coating is enhanced by above 150% in comparison with the conventional coating.