The invention provides a laser welding method for a thin-walled tantalum tube and a thin-walled iron-nickel alloy pipe. The laser welding method comprises the following steps of: 1, microscopically, removing burrs of the thin-walled tantalum tube and the thin-walled iron-nickel alloy pipe, and after grinding and polishing, carrying out ultrasonic washing; 2, assembling before welding to obtain an assembly part; 3, placing the assembly part in a welding chamber of laser equipment, aligning a laser generator with a welding hole to enable a laser beam emitted by the laser generator to be irradiated to to-be-welded positions of the thin-walled tantalum tube and the thin-walled iron-nickel alloy pipe, installing a chuck on a lathe, then closing the welding chamber, filling inert protection gas by a gas inlet pipe, rotating a rotating shaft by the lathe, and simultaneously emitting the laser beam to obtain a welded structure of the thin-walled tantalum tube and the thin-walled iron-nickel alloy pipe. The laser welding method can overcome the deficiencies and the defects of part deformation, burning loss of an iron-nickel alloy part, runoff and evaporation in the process of welding tantalum and iron-nickle alloy thin-walled parts in the prior art, and is particularly suitable for high-strength connection of the tantalum and iron-nickle alloy thin-walled parts.