The work aims to optimize the laser remelting process of 4Cr5MoSiV1 steel fabricated by selective laser melting (SLM), and comprehensively improve the mechanical properties of 4Cr5MoSiV1 steel. The 4Cr5MoSiV1 steel sample was fabricated by adjusting the parameters of laser remelting during SLM, and the surface morphology, microstructure, microhardness, tensile strength, elongation after fracture and wear resistance of the sample were tested and analyzed by SEM, microhardness tester, universal material tester and wear tester. The 4Cr5MoSiV1 steel fabricated by SLM had many splashing particles, impurity particles and curved corrugations on the surface, with microhardness of 599HV, tensile strength of 1050.2 MPa, elongation after fracture of 9.5% and wear rate of 1.309×10?10 kg/(N.m). After laser remelting, the metallurgical quality of 4Cr5MoSiV1 steel sample was obviously enhanced, with microhardness, tensile strength, elongation after fracture and wear resistance improved well, and there was a positive correlation between the mechanical properties. The mechanical properties of 4Cr5MoSiV1 steel were determined by metallurgical quality and fine grain strengthening. With the increase of line energy density of laser remelting, the mechanical properties of 4Cr5MoSiV1 steel increased firstly and then decreased. When the line energy density of laser remelting was 238 J/m, the mechanical properties of the sample were the highest, with microhardness of 645HV, tensile strength of 1430.7 MPa, elongation after fracture of 16.9%, and wear rate of 0.354×10?10 kg/(N.m). The fracture mechanism of 4Cr5MoSiV1 steel fabricated by SLM was brittle cleavage fracture, and that of laser remelted 4Cr5MoSiV1 steel was quasi cleavage fracture. The wear mechanism of 4Cr5MoSiV1 steel formed by SLM and laser remelting was mainly adhesive wear and oxidation wear. The optimal energy density of laser remelting line for SLM forming 4Cr5MoSiV1 steel sample is 238 J/m. The metallurgical quality and mechanical properties of the sample after laser remelting are obviously improved.