The invention discloses an injection pump device for an immunohistochemical staining apparatus, and aims to provide the injection pump device which can effectively solve the problems of infiltration and spattering of liquid reagent inside an injector under a pressure action due to loosening of a connection structure between the syringe and a distributor. The device comprises a locking buckle, a rack, and the distributor and the injector arranged on the rack. The distributor comprises a distributor body arranged on the rack and a vertical connection sleeve arranged on the distributor; the syringe comprises a vertical syringe positioned under the distributor; a syringe connection sleeve is sleeved at the upper end of the syringe; the upper part of the syringe connection sleeve is arranged in the vertical connection sleeve; the syringe connection sleeve is connected with the vertical connection sleeve by threads. The locking buckle comprises a locking bolt, a locking buckle body, a locking hole which is formed in the locking bucket and penetrates through the upper end surface and the lower end surface of the locking buckle body and two distributor limiting blocks which are arranged on the upper end surface of the locking buckle body.