Abstract: Two kinds of WC-10Co-4Cr coatings with different particle-density were deposited on 300M steel by high-velocity oxygen fuel (HVOF) technology. The microstructure and properties of WC-10Co-4Cr coatings were assessed by scanning electron microscope (SEM),X-ray diffraction (XRD) and micro-hardness tester. The corrosion resistance of the two kinds of coatings in a 3.5% NaCl solution was investigated by polarization test and immersion test. The results indicated that the porosity ratio of high particle-density coating was 1.52%,which was 1.95 times as big as that of low particle-density coating. In the NaCl solution,the value of passivation current density of high particle-density coating was 3.2 μA/cm²,which was 2.67 times as big as that of low particle-density coating. Therefore,low particle-density coating exhibited superior corrosion resistance than high particle-density coating due to its less porosity.