The invention relates to the technical field of instrument equipment, and discloses a splicing type fixing device for an automatic instrument. The splicing type fixing device comprises a mounting plate and an instrument body arranged on the front side of the mounting plate, wherein a rectangular hole is formed in the middle of the front side wall of the mounting plate, a fixing block is slidably connected to the interior of the rectangular hole, the front side wall of the fixing block extends to the outside of the rectangular hole and is fixedly connected with the rear side wall of the instrument body, clamping blocks are symmetrically and fixedly connected to the left end and the right end of the lower side hole wall of the rectangular hole, first clamping grooves matched with the two clamping blocks are respectively formed in the left side and the right side of the lower end of the fixing block, a first cavity is formed in the position, located on the upper side of the rectangular hole, of the interior of the mounting plate, and second cavities are symmetrically formed in the positions, located on the left side and the right side of the first cavity, of the interior of the mounting plate. According to the splicing type fixing device, the instrument can be preliminarily positioned conveniently during installation, so that the instrument is not prone to falling onto the groundto be damaged, the instrument can be conveniently disassembled during maintenance, the time and labor are saved, and the efficiency is high.