This paper takes GH738 alloy parts as the research object, analyzes the effect of additive repair on the heat treatment and mechanical properties of GH738 alloy. Compared with the matrix, the size of γ 'phase in the heat affected zone increases significantly, its average size increases from 50 nm to 110 nm, and the average spacing increases significantly; the carbide content decreases in the heat affected zone, and some carbides decompose, The fracture micro morphology of laser deposition repair sample belongs to ductile fracture. After aging, the grain boundaries of the as deposited dendrites began to expand and merge, and new grains formed at the same time. After aging treatment, there are a lot of γ′ phase precipitated in the repair area, and the γ′ phase continues to grow with the increase of aging temperature, but the content of γ 'phase changes little. Compared with the deposited state, the tensile strength of the sample increased significantly after aging heat treatment, but the plasticity decreased; the plasticity of the repaired sample decreased with the increase of the effective temperature at any time. When the carbide on the grain boundary precipitates in the form of coating, the crack on the grain boundary propagates rapidly along the carbide on the grain boundary, and the mechanical properties of metal are seriously reduced.