The invention relates to a medical knee bending lower limb moving brace, which is structurally characterized in that a support rod is connected with a tray, the tray is connected the lower part of a support pad, the support pad is in a U-shaped structure and comprises a bottom plate, a front plate and two side plates, the bottom plate is in a rectangular shape, the width of the bottom plate is the width of the crus of a human body, the length of the bottom plate is two thirds of the outer length of the crus length, the front plate is in a rectangular shape, the width of the front plate is coincident with that of the bottom plate, the height of the front plate is two thirds of the thigh length of the human body, each side plate is in a ladder shape, the height of each side plate adjacent to the front plate is coincident with that of the front plate, the length of each side plate adjacent to the bottom plate is coincident with that of the bottom plate, an upper side is an inclined side, the length of a short side is two thirds of the height, and a height regulating handle is connected with the tray. The medical knee bending lower limb moving brace overcomes the defects of stiffness of knee joints and hip joins, thigh and crus muscular atrophy, disuse osteoporosis of thighbones and shin bones, the risk of deep venous thrombosis occurrence at an affected limb side. The medical knee bending lower limb moving brace has the advantages that the positions lower than the intralesional knee joint are protected, and complications, such as venous thromboembolism, amyotrophy and disuse osteoporosis, caused by lower limb braking are prevented and controlled.