The invention discloses a device for assembling a lamp plate to an iron frame. The device comprises a base, and further comprises a left support assembly, a right support assembly, a rotary platform and a lamp plate positioning mechanism, wherein the left support assembly and the right support assembly are located at the left end and the right end of the base respectively and can rotate, the rotary platform is fixed on the left support assembly and the right support assembly, and the lamp plate positioning mechanism is located at the upper left corner of the rotary platform; a longitudinal positioning area is arranged on the rear side of the rotary platform, a left positioning area is arranged on the left side of the rotary platform, a right positioning area is arranged on the right side of the rotary platform, the middle of the rotary platform is an iron frame placement area, and a plurality of strip-shaped grooves are formed in the lower side of the iron frame placement area; and theleft support assembly comprises a support, and a rotary block which is rotationally connected to the right side of the support through a rotary shaft, the upper end of the rotary block is fixedly connected with the middle of the left side of the rotary platform, and the bottom of the support is fixed at the left end of the base. According to the scheme, the structural design is simple and practical, the positioning effect is accurate, the operation is fast, and the efficiency of attaching the lamp plate is greatly improved.