The invention discloses an auxiliary hoisting device special for steel grating structure plant construction. The auxiliary hoisting device comprises a hoisting tool, a strengthening support, a bearing steel plate and a bolt; the hoisting tool comprises a hoisting arm, the upper end of the hoisting can penetrate steel grating and is provided with a bolt hole, and a hoisting ring is integrally molded at the bottom end of the hoisting arm; the strengthening support is paved on the steel grating, and therefore the stress area of the steel grating is increased; a penetration gap allowing the upper end of the hoisting arm to penetrate conveniently is formed in the strengthening support; the bearing steel plate is flatly placed on the strengthening support, and a penetration hole allowing the upper end of the hoisting arm to penetrate conveniently is formed in the position, corresponding to the penetration gap, on the bearing steel plate; the bolt and the hoisting tool are correspondingly arranged, the bolt is inserted into the bolt hole, and therefore detachable connection between the hoisting tool and the bearing steel plate is achieved. The auxiliary hoisting device is simple in structure, convenient to mount and demount and easy to manufacture, the hoisting safety of a construction site can be greatly increased, and the hoisting speed of the construction site can be greatly increased.