The utility model discloses a self-feedback power unscrewing device of an underwater winch. The device comprises a sealed cabin, a front end cover and a rear end cover are respectively mounted on twosides of the sealed cabin; the front end cover, the rear end cover and one end of the sealed cabin sealing shaft are fixedly arranged on the inner ring of the electric slip ring; the other end penetrates out of the sealed cabin through the front end cover; the sealing shaft and the front end cover are dynamically sealed through an O-shaped ring; in addition, the sealing shaft is further in transmission connection with an input shaft of the encoder through a gear, an inner ring wire of the electric slip ring penetrates through an inner hole of the sealing shaft to be electrically connected withthe watertight connector outside the sealed cabin, then the inner hole of the sealing shaft is filled with epoxy resin pouring sealant, and an outer ring wire of the electric slip ring is electrically connected with the watertight connector installed on the rear end cover. According to the self-feedback power unscrewing device, the motor, the speed reducer, the electric slip ring, the band-type brake device and the absolute encoder are innovatively designed into a whole, the self-feedback power unscrewing device can be used for underwater 500-meter water depth, watertight connectors are designed at the two ends of the self-feedback power unscrewing device, and therefore the self-feedback power unscrewing device becomes an independent module capable of being independent of an underwater winch.