The invention belongs to the field of hydraulic devices, and particularly discloses a hydraulic device having a real-time position self-locking function. The hydraulic device comprises a rotating piston assembly, a fixed piston assembly and a hydraulic oil cylinder; the rotating piston assembly comprises a driving motor, an inner piston rod and a rotating piston; the driving motor is fixed to a motor locating flange; an output shaft of the driving motor is connected with one end of the inner piston rod through a coupler; the other end of the inner piston rod is connected with the rotating piston; the fixed piston assembly comprises an outer piston rod and a fixed piston; the inner piston rod is sleeved with the outer piston rod; the two ends of the outer piston rod are connected with the motor locating flange and the fixed piston correspondingly; the fixed piston and the rotating piston as a whole are located in the hydraulic oil cylinder; convection holes are formed in the fixed piston and the rotating piston; and the convection holes formed in the convection holes communicate or not in the rotating process of the rotating piston, and then unlocking or locking of the hydraulic device is realized. The real-time position self-locking function can be realized, and the hydraulic device has the advantages of control simplicity and convenience, simple structure and the like.