The invention discloses an infusion cap screwing device used for a genetic engineering preparation processing production line. The infusion cap screwing device comprises an upper sleeve box, a conveying table, a lower containing cabinet, a lifting seat, a preparation injection disc and clamping and supporting tables. The upper sleeve box is of a hollow cuboid structure, and the conveying table ishorizontally arranged below the middle portion of the upper sleeve box. The conveying table and the upper sleeve box are arranged in a penetrating manner. The infusion cap screwing device has the beneficial effects that a third motor is used for driving three clamping pieces to clamp the side wall of a bottle cap of a preparation containing bottle through a swing shaft, the cap is screwed in a rotating manner, the preparation containing bottle is sealed, the device can screw and seal the bottle cap immediately after preparation injection of the preparation containing bottle is conducted, the work efficiency of the device is improved, the phenomenon that after preparation injection, in the process that the preparation containing bottle is transferred to the cap screwing device, the preparation is spilled out from a bottle body or the preparation in the bottle body is volatized is avoided, it is ensured that the genetic engineering preparation is injected more sufficiently, and sprinkling waste is avoided; and in addition, the three clamping pieces are distributed in an arc manner, the force applying effect of the clamping pieces on the bottle cap is higher, the cap screwing efficiency is higher, and the quality is better.