Abstract: In the article the segment-based and self-capacitive displacement sensor was designed,the interval displacement between the sliding plate and the covered fixing plate was measured by capacitive measuring circuit, the relative edge displacement between the two plates was computed by the ratio method, and the total length of the displacement sensor was the sum of the length to be measured and the length of the sliding plate. The measuring accuracy of the displacement sensor was improved and the measurement error less than the maximum value measured between the sliding plate and one fixing plate, under the existing degree of the circuit. The effect on the measured error by the parameters of the insulator thickness and the dielectric constant was eliminated.