The invention discloses a welding fixture for a nuclear fuel assembly positioning grillwork, and relates to the welding technology of the nuclear fuel assembly positioning grillwork. The welding fixture aims at solving the problems that a conventional welding fixture is complex in structure, the design accuracy is worse, and the welding quality is influenced. A follow fixture comprises a square frame defined by four positioning plates, and the length and the width of the square frame are adjustable; each positioning plate is provided with a positioning pin, an upper row of light through holes and a lower row of light through holes; and a sleeve fixture comprises an upper cover plate and a base plate, a through hole is formed in the position, corresponding to a sleeve, on the base plate, a plum-blossom-shaped hole is formed in the position, corresponding to the sleeve, on the upper cover plate, and four symmetrically-arranged protrusions are installed on the periphery of the plum-blossom-shaped hole. The welding fixture is simple in structure and easy to machine, and the welding requirement can be completely met; compared with a conventional welding manner and a conventional welding fixture, the welding quality can be greatly improved; and the follow fixture serves as a transition structure for assembling and welding the fixture, the conversion continuity of the two parts is guaranteed, all welding seam connection can be completed at a time, and the welding fixture is suitable for welding of the nuclear fuel assembly positioning grillwork.