In the paper, nanostructured, multimodal and conventional WC-12Co cermet coatings were sprayed by HVOF and the properties and structures of the coatings such as microhardness, microstructure, phase composition were compared. Finally sand solid and slurry erosion wear tests were carried out and their wear failure mechanisms were explored by XRD and SEM analysis. Research results show that microstructures of nanostructured and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity, and their microhardness values are obviously higher than conventional WC-12Co coating. As well, it was found that nanostructured and multimodal WC-12Co coatings exhibited better sand solid and slurry erosion wear resistance in comparison with conventional coating and nanostructured WC-12Co coatings possessed the best sand solid erosion resistance properties at large impact angles and slurry erosion wear resistance. Testing results also show that although decarburization of WC occurred during spraying multimodal and nanostructured WC-12Co powders, the decarburization of WC for the nanostructured powder was more severe.