Improvement of wear and corrosion resistance by coating processes is a necessity for magnesium alloys. In the present study, 420 stainless steel coatings reinforced with WC–17Co particles were deposited on commercial AZ80 magnesium alloy using the cold spraying technology. Effects of WC–17Co content on microstructure, wear behaviour and corrosion resistance of the cold sprayed composite coatings were studied. Experimental results show that the composite coatings possess higher microhardness and more excellent wear resistance than magnesium alloy substrate. The microhardness and wear resistance of the composite coating are evidently improved with the increase of WC–17Co particle content. Meanwhile, 420SS/WC–17Co composite coatings also reduce the corrosion current density of magnesium alloy, despite that corrosion resistance of the composite coating declines to some extent at a higher content of WC–17Co. Finally, cold sprayed 420SS/WC–17Co composite coating is successfully applied to increase the durability of magnesium alloy road wheel of tracked vehicle.