Abstract: For GH3128/GH3536 nickel-based superalloys, a study was conducted on the formation quality, microstructure, and properties of laser-welded T-type lap joints. The effects of laser power, welding speed, and defocusing amount on weld surface formation, internal porosity defects, and weld dimensions were systematically analyzed. Ultimately, high-quality joints with a large depth-to-width ratio and no porosity defects were obtained, with the optimized process window as follows: laser power of 2 400 ~ 2 800 W, defocusing amount of + 10 mm, and welding speed of 2.43.0 m/min. EBSD analysis shows that the grain size of the GH3128 base metal is 17.28 µm, and that of its weld zone is 31.25 µm; the grain size of the GH3536 base metal is 22.52 µm, and that of its weld zone is 27.71 µm, with a grain size of 14.55 µm in the fine-grain region. Pole figure analysis indicates that the welds on both sides have different texture characteristics. The 100 and 111 crystal planes on the GH3128 side exhibit obvious preferred orientation, while the texture distribution on the GH3536 side is relatively dispersed. KAM analysis shows that the KAM value in the weld zone is higher than that in the base metal zone, indicating a higher local strain in the weld. Moreover, the strain distribution in the GH3536 weld zone is more concentrated and uneven. EDS result analysis indicates that obvious segregation of Fe element appears near the fusion line on the GH3536 side, with its content decreasing by approximately 14%. The hardness distribution of this weld gradually increases from the base metal to the weld center, which is significantly different from the weld hardness on the GH3128 side.