The invention provides an active and passive joint prosthesis mechanism, which comprises an active driving mechanism, a passive constraining mechanism, a knee joint shaft, an overrun clutch and the like. The active driving mechanism consists of a direct current servo motor, a reducer and a gear. The passive constraining mechanism consists of a direct current servo motor and a bevel gear shaft. The knee joint shaft is mounted on a U-shaped block consisting of a left side plate, a right side plate and a top plate. The knee joint shaft is provided with the bevel gear; a star wheel of the one-way overrun clutch and the shaft are fixedly connected by key connection; and the external ring of the clutch is fixedly connected with a cylindrical gear. The relationship between the active driving mechanism and the passive constraining mechanism is established by the mesh of two cylindrical gears, namely, one of the active driving mechanism and the passive constraining mechanism drives the star wheel of the clutch and the other one drives the external ring of the clutch. When a user of the prosthesis walks, under the control and coordination of a prosthesis control system, the active driving mechanism conducts an active driving function and the passive constraining mechanism conducts a passive constraining function.