In order to increase the surface hardness and wear resistance of the GCr15 steel, as well as reduce the energy consumption and improve the traditional quenching environment, laser quenching is carried out on GCr15 steel with a 400 W fundamental-mode fiber laser. The effects of scanning speed and defocusing amount on the quenching layer are analyzed. The microstructure of the hardened region consists of fine martensite and a few spheroidal carbide. The microhardness increases with the increase of scanning speed and then decreases, and the same for the defocusing amount. The microhardness of GCr15 steel is 960 Hv after being quenched with fiber laser power of 400 W, scanning speed of 0.6 mm/s and defocusing amount of 0, which is 4.4 times of that of the matrix. The wear resistance of GCr15 steel quenched by fiber laser is significantly improved. The wear mechanism is mainly oxidation wear, mechanical wear and abrasive wear.