The laser butt welding experiments of Inconel625 and 316LN dissimilar material alloy tubes were carried out, and the joint morphology, microstructure, chemical composition and mechanical properties of each sample were analyzed. The experimental results show that the weld is in good shape under the laser power of 1 100 to 1 300 W, the defocus of + 20 mm and the welding speed of 870 mm/min and 20 L/min 99.9%Ar gas protection, and the all-position welding of Inconel625&316LN thin-walled alloy pipe is realized with less internal defects. The transition of interface elements between Inconel625&316LN weld and base metal is obvious. Due to the mutual solubility of Fe and Ni, it is mainly composed of Fe and Ni solid solution with atomic ratio close to 1∶1 in the weld. The tensile strength of the laser welded joint of Inconel625&316LN pipe is higher. Due to the uniform distribution of Fe and Ni solid solution in the weld and the solid solution formed by the mutual dissolution of Fe and Ni elements in nickel and steel, the weld strength is higher, and it is not lower than that of the base metal, and it will not give priority to cracking under tensile test. With the increase of heat input, the crystal size in the weld gradually increases, the yield strength of the weld decreases gradually, and the fracture form is mainly the ductile fracture of the base metal.