To guarantee the comprehensive mechanical properties of laser additive repaired 15-5PH parts can meet the operating requirements, laser cladding experiment is carried out with optimized process parameters, and the microstructure and mechanical properties of cladded layer and heat affected zone (HAZ) are analyzed. Results shows that the microstructure of the cladded layer is columnar dendrite growing perpendicular to the track joint. In addition to Martensite, there are a small amount of residual austenite and ferrite. The average microhardness of the cladded layer is about 355 HV, showing relatively high strength and plasticity while yield strength is low. Microstructure are refined in phase transformation zone, and microhardness increased gradually from the bonding interface, reaching peak value (about 420 HV) at the depth of 0.5 mm. High-temperature tempered area are found below phase transformation zone, in which microhardness decreases to about 360 HV and gradually restore to the level of substrate. Tempered area is narrow, which has little influence on the mechanical properties of the substrate. The plasticity of the sample in HAZ is slightly improved while maintaining high tensile strength. The tensile properties of the laser additive repaired sample (with 50% cladded layer in thickness) is close to that of the heat treated substrate.