The invention provides an insert assembly machine which comprises a positioning plate, a power mechanism and a fixed block for fixing a shell. The positioning plate is provided with a sliding groove. The power mechanism comprises a power device and a pushing block installed at the output end of the power device. The pushing block is slidingly connected to the sliding groove. An insert is pushed by the pushing block to slide in the sliding groove. The sliding groove is provided with a feed port whose width is larger than that of the insert. The output end of the feed port and the sliding groove are connected in a tapered transition mode. The fixed block is fixedly installed at one end of the sliding groove. The fixed block is provided with a profiled groove which is matched with the shape of the shell, and the opening of the profiled groove part is corresponding to the sliding groove. When the insert assembly machine is used, the insert is placed into the feed port, the insert shell is installed in the profiled groove of the fixed block, the power device drives the pushing block to slide in the sliding groove, the insert is in contact with the insert shell in the fixed block and is inserted into a shell cavity, a purpose of assembly is achieved, the device is simple, and the operation is easy.