The　WC-10Co-4Cr　composite　powder　was　synthesized　firstly.　Then　the　composite　powder　was　agglomerated　to　prepare　thermal　spraying　feedstock.　The　ultrafine/nanostructured　WC-10Co-4Cr　coating　was　prepared　by　high　velocity　oxygen　fuel　thermal　spraying.　The　phase　constitution,　elemental　distribution　and　microstructure　of　the　coating　were　characterized　by　X-ray　diffraction　and　transmission　electron　microscopy,　respectively.　The　wear　resistance　and　corrosion　resistance　of　the　prepared　composite　coating　were　tested.　The　results　show　that　the　main　phases　of　the　coating　include　WC,　binding　phase　with　partial　amorphous　structure,　with　a　little　W2C　and　Co(Cr)　coexisting.　The　distributions　of　Co　and　Cr　elements　from　the　phase　boundary　to　the　eutectic　area　then　to　Co　zone　were　analyzed　quantitatively.　The　mechanisms　for　the　formation　of　the　microstructure　and　effects　of　Cr　on　the　performance　of　the　composite　coating　are　proposed.