A full-automatic lifting system with a protective jack can be a combined type mechanical lifting unit, and can adopt a posture-maintaining full-automatic lifting mode. An angle sensor is mounted on a lambdoidal door, lifting units with displacement sensors lift, the angle sensors transmit inclination change data of the lambdoidal door to a PLC (programmable logic controller), by the aid of contrast operation, the PLC instructs the lifting units of an X axis and a Y axis which are adjacent to a track, and the purpose that the lambdoidal door lifts at the same posture is achieved. Furthermore, the full-automatic lifting system is provided with the mechanical automatic tracking protective jack, each displacement sensor is arranged between a corresponding big gear wheel and a corresponding screw seat, screws are driven to vertically move in the screw seats along with lifting of cylinders, when larger than or smaller than a set value, the data of the displacement sensors are transmitted to the PLC, by the aid of contract operation, the PLC instructs corresponding motor retarding mechanisms to drive pinions so as to drive the big gear wheels to move, nuts on the big gear wheels vertically move on the screws, and purposes of maintaining a set gap between each nut and the corresponding screw seat and automatically tracking the projective jack in a lifting process are achieved.