WC/Co- Y2O3 alloying layers are prepared by laser alloying on 38CrMoAl steel substrate. The influences of Y2O3 mass fraction on microstructure and properties of the layers are investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester, and friction wear testing machine. The results show that the layers with different mass fractions of Y2O3 are mainly consist of austenite, martensite, Fe3W3C and WC phases. With the increase of the Y2O3 addition, the contents of the Fe3W3C, nano- WC, and austenite gradually increase, whereas the content of martensite gradually decreases. But when the mass fraction of Y2O3 is more than 1.0% , the content of the nano- WC begins to decrease, the solidified microstructure is slightly coarsened. Because of these changes in the microstructure, the hardness and wear resistance of the layers first increase and then decrease, that is, the layer has the highest hardenss and the better wear resistance as the Y2O3 mass fraction is 1.0%.