Continuous lowering device for large steel casing

The utility model provides a continuous lowering device for a large steel casing. The device comprises a base which is provided with a lowering channel and comprises a mounting frame; the lowering mechanism comprises a fixing part which is arranged below the mounting frame and is used for being fixed on the steel casing; the supporting seat is arranged above the mounting frame, and a movable cavity is formed in the supporting seat; the center hole jack is arranged above the supporting seat; the limiting parts are arranged above the center hole jack at intervals; the deformed steel bar extends up and down, and the deformed steel bar sequentially and movably penetrates through the limiting part, the center hole jack and the mounting frame and is connected with the fixing part; the first nut is in threaded connection with the deformed steel bar and is located between the limiting part and the center hole jack; the second nut is in threaded connection with the deformed steel bar and is located in the movable cavi