An absolute position measurement capacitive grating displacement sensor, comprising a transmission board and a reflection board capable of moving relative to each other and a measurement circuit, wherein a column of periodically arranged electrodes are disposed on the transmission board in a measurement axis direction, which form a transmission grating (1.1); a column of periodically arranged electrodes are disposed on the reflection board in the measurement axis direction, which form a reflection grating (2.1); two columns of periodically arranged electrodes orderly connected to the reflection grating (2.1) are further disposed on the reflection board, which form a conversion grating; two columns of periodically arranged electrodes for capacitive coupling with the conversion grating are further disposed on the transmission board, which form a reception grating; each N electrodes of the transmission grating (1.1) form a group, N is an integer, 3≤N≤16, the electrodes are periodically arranged at intervals of P t /N, an electrode pitch of the transmission grating (1.1) having N electrodes in a group is P t, P t is Nt times of a fine wavelength W f, and Nt is an odd number between 3 and 7; the electrodes of the reflection grating (2.1) are divided into two groups alternately and periodically arranged at intervals of P r, where P r =W f, the conversion grating electrodes on the reflection board are arranged along the measurement axis at respective intervals periodically, the two groups of electrodes of the reflection grating (2.1) are orderly connected to the two columns of conversion grating electrodes respectively by wires; the measurement circuit comprises an interface unit and a measurement unit; the interface unit comprises a timer, a keyboard interface circuit, a measurement interface circuit, a display drive circuit, and an Arithmetic Logic Unit; and the measurement unit comprises a drive signal generator and a signal processing circuit; wherein the measurement unit further comprises an oscillator, a frequency divider, and a controller; the drive signal generator is a drive signal generator for generating a sensor drive signal having wave properties; a master clock output by the oscillator of the measurement unit is connected to the drive signal generator through the frequency divider; N output signals of the drive signal generator respectively are connected to N electrodes in each group of the transmission grating (1.1); the signal processing circuit of the measurement unit comprises an analog processing circuit, a zero-crossing detection circuit, a synchronous delay circuit, an addition counter, a synchronous capture circuit, and a Random Access Memory; the analog processing circuit comprises a signal selection switch group, a differential amplifier, a synchronous demodulation circuit, and a low-pass filter; two outputs of the reception grating of the measured wavelength are connected to the differential amplifier through the signal selection switch group, after differential amplification, are then successively connected to the synchronous demodulation circuit, the low-pass filter, and the zero-crossing detection circuit, and then are input into the synchronous capture circuit; the master clock output by the oscillator is further connected to the controller, the synchronous demodulation circuit, the synchronous capture circuit, and the addition counter; a phase synchronization signal of the drive signal generator is connected to the synchronous delay circuit; an output of the synchronous delay circuit is connected to the synchronous capture circuit and the addition counter; an output of the zero-crossing detection circuit is connected to the synchronous capture circuit, an output of the synchronous capture circuit is input into the controller and the RAM at the same time, an output of the addition counter serves as a data input of the RAM; the measurement interface circuit of the interface unit is connected to the controller of the measurement unit and the RAM; and outputs of the controller generating various control signals respectively are connected to the RAM, the drive signal generator, the signal selection switch group, and the measurement interface circuit of the interface unit; an input terminal of the controller is connected to an output terminal of the synchronous capture circuit, and the master clock output by the oscillator is connected to a clock input terminal of the controller.