The invention discloses a knee joint function training device. The device comprises a rack, a supporting device, a driving device, a fixing pressing device and a control device; the supporting devicecomprises a supporting frame slidingly connected with a shell and vertically arranged, a foot fixing sleeve rotatably connected with the supporting frame, a calf placement frame rotatably connected with the upper end of the supporting frame and located at the side close to the upper limb of a patient and a thigh placement frame rotatably connected with the end, away from the foot fixing sleeve, ofthe calf placement frame; the other end of the thigh placement frame is rotatably connected with the end, close to the upper limb of the patient, of the shell; the fixing pressing device comprises afirst airbag belt, a second airbag belt and an intermittent inflation pressure pump; since the lower limb of the patient is subjected to isometric contraction and isotonic contraction which are closerto the physiological movement of the human body simultaneously, the venous blood flow stasis is relieved, the venous thrombosis is prevented, and the recovery of the patient is facilitated; due to the addition of the isometric contraction in the whole isotonic contraction process, part of attention of the patient in the pressurization and pressure relief process is distracted, and the pain brought to the patient is reduced.