Two kinds of harding coatings: WC-12Co and CrC-25NiCr were made by active combustion-high velocity air flue (AC-HVAF). By the rotating disc test rig, the systematical experiments were carried to study the wear resistance and mechanisms of coatings on different test conditions: pure water cavitation and sandy water silt erosion. On the sandy water silt erosion test condition, the wear resistance of HVAF coatings is better than that of metal matrix. However, it is reverse on the other test condition. Basing on the scanning electron microscope (SEM) analysis, the surface morphology of coating surface after wear was studied. And the influence of adhesion strength, micro-hardness and porosity ratio of HVAF coating on wear resistance was researched in detail.