The invention relates to an angular displacement sensor, belonging to a sensor for measuring rotating angle. The angular displacement sensor solves the problem that the existing rotary potentiometer is hard to install when in angle measurement, and comprises a fixed component and a rotating component, wherein the fixed component includes an insulating base body and a conductive carbon film layer, and the circular-arc-shaped conductive carbon film layer provided with a nick is adhered to the surface of the ring-shaped insulating base body; the two circular-arc-shaped ends of the conductive carbon film layer are respectively provided with a positive electrode and a negative electrode; a signal output pole is arranged at the position corresponding to the circular-arc-shaped nick of the conductive carbon film layer on the insulating base body, and is welded with a V-shaped copper probe; the rotating component includes an insulating ring, a copper ring and an electric brush, wherein the copper ring is embedded and sheathed at the outer circumference of the insulating ring, and provided with the electric brush. The angular displacement sensor has simple and compact structure, can be directly sheathed on a rotating shaft, does not need an extra special sensor mounting box, can work in high pressure hydraulic oil, and is especially suitable for joint rotation angle measurement of an underwater robot, an underwater engineering machine and other underwater equipment.