In this paper, an on-orbit calibration method based on distortion gradient reconstruction distortion is proposed. It makes full use of the star spacing measurement technology with the measurement accuracy of micro arc seconds, thus it does not need to use star catalogue, and is not limited by the accuracy of stellar right longitude and declination. The calibration accuracy of optical distortion of the telescope can reach the order of micro arc seconds. The principles of distortion reconstruction based on distortion gradient are introduced, and the distortion calibration simulation experiment is carried out on the optical system derived from the optical design software. The results show that when the wave aberration of the optical system is controlled within 0.0733λ and the measurement error of star angle spacing is 0.3 micro arc seconds, the distortion calibration accuracy can reach 0.28 micro arc seconds, which meets the distortion calibration requirements of nearest neighbor habitable planet exploration.