Abstract. The microstructure, hardness and corrosion resistance of the tungsten alloy hardened layer, which was hardened by different power of electrospark, were investigated. The results show that the matrix and the electrode of the tungsten alloy were melted into each other after hardened by electrospark. The hardness and corrosion resistance of the hardened layer were significantly improved, and had a significant correlation with the power of the electrospark. The hardness of the hardened layer under 1600W is the largest, which improved 35.3% than the matrix. The corrosion current density of 2000W is the smallest, which is about 0.17 A/cm 2 , and is decreased by almost two orders of magnitude than the matrix material. A dense oxide film was formed on the surface of the hardened layer in the case of the electrospark power of 2000W.