In order to study whether the properties of the repairing layer can meet the work needs after laser additive repair of lCrl5Ni4Mo3N, the mechanical properties and microstructure of laser additive repair of lCrl5Ni4Mo3N was conducted. WDW-100 testing machine was used to test the tensile strength of samples. The OM and SEM were used to survey and analyze the microstructure and fracture morphology of the joints. Research indicates that the forming of the laser additive repair of lCrl5Ni4Mo3N is good. The tensile strength of 2 mm deep repairing sample can reach 92.7% of the base material, the tensile strength of 3 mm deep repairing sample can reach 89.7% of the base material. The repairing joint shows ductile fracture. Due to coarsening of second-phase particles caused by laser thermal cycle, the microhardness value of microstructure are: base material＞repairing layer＞HAZ. The metallurgical combination of repairing layer and substrate is dense. The joint consists of base material，HAZ and repairing layer. The base material is mainly composed of tempered martensite and contains retained austenite,the HAZ is mainly composed of tempered martensite and contains tempered sorbite, and the repairing layer consists of a martensite and austenite dual-phase structure.
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