The GH738 nickel-based superalloy through-groove sample is repaired by laser deposition, and the microstructure and room temperature tensile properties of the repaired sample are analyzed. The results show that the microstructure of repair zone presents typical characteristics of columnar dendrite with epitaxial growth, and the dendrites are perpendicular to the substrate and tend to grow along the deposition height direction through multiple layers. The dendritic orientation in the center of the repair area shows a large deflection. No γ′ phase is found in the repair area, the content of carbide in the area is less, the M23C6 type carbides rich in Cr and Co mainly exist in the dendrite stem, and a few cubic MC carbides with relatively larger size and higher contents of Ti and Mo exist among the dendrites. Compared to the substrate, the size of γ′ phase in the heat affected zone obviously increases, the size of partial γ′ phase exceeds 200 nm and the average distance between them increases obviously. The content of carbide in the heat affected zone reduces, and partial carbides decompose. The room temperature tensile strength and elongation of the laser deposition repair sample is 78.2% and 69.2% of those of the forging, respectively.