In order to solve the problem of frequent calibration of nonlinear error for capacitive displacement sensors in micro-thrust measurement, an in-situ calibration method based on laser interferometry is studied. The calibration principle is that the optical path difference and capacitive displacement sensor plate spacing are changed simultaneously by adjustment and measurement of the positions of movable corner prism and object through the linear displacement, and the nonlinear error of sensor is calibrated by the linear fitting method based on the measuring results of laser interference. The interferometric optical path based on common optical elements is built and sensors with different measuring ranges are calibrated in micro-thrust measurement. Based on the analysis of characteristics of the interference intensity, the calculation method of interference fringe number is determined. The measuring accuracy of interference light path displacement is 66.5 nm. The practicability and accuracy of the calibration device are verified by experiment. Finally, the results of calibration, the nonlinear sensor output relative error and the main factors affecting the laser interference measurement accuracy are analyzed. The total error is 67.2 nm.