The invention discloses an angular displacement sensor based on atomic force. The angular displacement sensor comprises a piezoelectric ceramic actuator base, a piezoelectric ceramic actuator, an atomic index dial, an atomic probe, a micro cantilever, a laser, a position sensitive photoelectric detector, an amplifier, a feedback controller and a computer. The piezoelectric ceramic actuator base is arranged at the center of the end face of a rotation shaft of a machine tool and controlled by the feedback controller and the computer. The atomic index dial is arranged on the piezoelectric ceramic actuator, and three labeled atoms are arranged on the surface of the atomic index dial. The micro cantilever is arranged above the atomic index dial, and the tail end of the micro cantilever is connected with the atomic probe and a reflector. After output lasers are reflected by the reflector, optical signals carrying labeled atom fluctuation positions are input to the position sensitive photoelectric detector and are amplified by the amplifier, and then are input to the feedback controller and the computer for storage and analysis. Before and after rotation of the machine tool shaft, position changes of the labeled atoms are scanned, the rotation angle of the shaft is obtained, and quick and accurate measurement of angular displacement can be achieved.