Abstract: The surface treatment of GW103K magnesium alloy was carried out by high current pulsed electron beam (HCPEB). The surface microstructure, hardness and corrosion resistance of the alloy after HCPEB treatment with different pulses (5, 15 pulses) were investigated. The results show that after HCPEB treatment, the surface of GW103K magnesium alloy had a large number of craters, pinholes and twins, and the β-Mg₅(Gd, Y) phase observed in original structure was dissolved in the matrix. The surface morphology and chemical composition of the alloy after 15-pulse HCPEB treatment were more uniform than those after 5-pulse HCPEB treatment. As the HCPEB pulses increased from 5 to 15, the thickness of the remelted layer on the alloy surface increased from about 7.67 μm to about 13.70 μm. After HCPEB treatment, the values at a distance of 50 μm to 250 μm from the surface was higher than that of the matrix, and reached the maximum values at a distance of about 70 μm from the surface. In the 3.5wt% NaCl solution, the free-corrosion current density of the alloy after 5-pulse HCPEB treatment was the smallest and the corrosion resistance was the best, ascribing to the dissolution of thorium and yttrium and the surface residual compressive stress.