In this work, WC-Co and WC-NiCr cermet coatings were deposited by high-efficiency supersonic atmospheric plasma spraying. The erosion resistance of both coatings was comparatively studied in normal or hot corrosion condition. Experimental results suggested that the decarburization happened during the spray of WC-Co or WC-NiCr powders, which led to the formation of W2C. Meanwhile, Co3W3C and Co6W6C were also found in WC-Co coating. Some new phases, such as W3C, W6C2.54, CoWO4 and WO3, were observed in WC-Co coating due to the decomposition and oxidation of WC during hot corrosion. WC-Co coating showed a higher erosion resistance than WC-NiCr coating, however, the erosion resistance of former significantly decreased after hot corrosion. On the contrary, the Cr2O3 that formed during hot corrosion can effectively protect WC from oxidation and thus improve the erosion resistance of WC-NiCr coating.