An angle sensor for measuring angular parameters of a rotary member includes a shaft, a rotary disc being connected to the rotary member and rotatable about the shaft, a number of electromagnetic elements disposed on the rotary disc, a precision controller electrically connected to the rotary disc for selectively magnetizing the electromagnetic elements, a magnetic sensor configured for sensing the magnetic field of the magnetized electromagnetic elements and generating sensing signals every time a magnetized electromagnetic element passes under the magnetic sensor, a mounting plate configured for mounting the magnetic sensor, the mounting plate being fastened to the shaft, and a calculator electrically connected to the magnetic sensor for receiving the sensing signals, the calculator being configured for calculating the angular parameters of the rotary member according to the received sensing signals, a corresponding elapsed time and the angle between adjacent magnetized electromagnetic elements.