The invention belongs to the field of nuclear fuel assembly machining and particularly relates to a device for assembling and supporting fuel assemblies.The device comprises a left support plate, a right support plate, a linkage articulation block and a pin shaft; one end of the left support plate is fixedly connected with the left end of the linkage articulation block through screws, one end of the right support plate is fixedly connected with the right end of the linkage articulation block through screws, a pin hole is formed in the middle of the linkage articulation block, and the pin shaft is arranged in the pin hole; the plate surface of the left support plate and the plate surface of the right support plate are each provided with multiple screw holes.By means of the device, the opening and closing angle can be adjusted automatically according to the overall dimensions of grillworks of the fuel assemblies, good contact of the assemblies can be achieved, and the effects of protecting and supporting the fuel assemblies are achieved.