Aiming at the drawbacks of the relative measurement, an absolute measurement technique using capacitive displacement sensor is presented in this paper. This technique is based on two coupling levels and multi-precision to achieve the absolute coding, which realizes the measurement of high accuracy and long-range. This paper gives a brief introduction of the structure of capacitive measurement system. And the principle of the system is also analyzed. Phase discriminator solves the problems that the accuracy of signals is decreased by the filter and long settling time is required.