An absolute position measurement capacitive grating displacement measurement method, a sensor, and an operating method of the sensor are provided. In the measurement method, a drive signal having wave properties is used to excite a transmission grating, and displacement of a measured position in each wavelength is transformed into an initial phase of a time fundamental wave. The displacement of the measured position in each wavelength is acquired through an addition counter. A signal having wave properties output by a drive signal generator of the sensor is connected to a transmission grating, the master clock of an oscillator is connected to each circuit, an output of a reception grating is connected to a synchronous capture circuit through a signal selection switch and an analog processing circuit; and the synchronous capture circuit is connected to a controller, an addition counter, and a Random Access Memory (RAM). The controller is connected to all components. In the operating method of the sensor, an interface unit starts a measurement unit, a controller coordinates operation of all circuits, and after measurement of displacements in coarse, medium, and fine wavelengths is successively completed, the interface unit turns off the measurement unit, performs processing, and displays the measurement result. The circuits are simple, easy to control, and easy to be realized, and have high precision.