The screw elevator uses a motor as the power source. The motor is connected to the nut through a belt, and the nut tooth pattern and the screw tooth pattern mesh between male and female. When the motor works, the nut is driven to move on the screw, thereby driving the car to move up and down.The structure of the yin and yang meshing between the nut tooth pattern and the screw tooth pattern greatly reduces the possibility of falling ladder.