Abstract: The invention provides a back-up brake system of lifts, which is inclusive of a back-up safety cable, guiding wheels and a brake, wherein four guiding wheels are mounted at the four corners of the lift car, the upper end of the back-up safety cable is fixed at the shaft way top, runs through the four guiding wheels and then its lower end is connected with the extension spring at the shaft way bottom; the brake is mounted in the middle of the car bottom, which is further inclusive of hydraulic wrenches and gear rope grippers. Operation of the system is such that the hydraulic wrenches run through the rope grippers and drive them to turn, while the back-up safety cable through the opening on the rope grippers, which the gear rope gripper in the upper and lower rows, turn in different directions to seize the back-up safety cable.