The relative astrometric method of microangular second measurement accuracy can be used to explore neighboring habitable planets. Accordingly, the in-orbit calibration accuracy of optical telescope payload distortion needs to reach the order of microangular seconds. The traditional on-orbit distortion calibration methods of optical telescopes generally rely on the star direction information, but the accuracy of star right longitude and declination in the existing catalogue is up to the order of milliseconds, which can not meet the requirements of micro-angle-seconds calibration. In this paper, an on-orbit calibration method based on distortion gradient reconstruction distortion is proposed. this method makes full use of the star spacing measurement technology of microangular second measurement accuracy, 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 microangular seconds. In this paper, the principle of distortion reconstruction based on distortion gradient is 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 0.0733 λ and the measurement error of star angle spacing is 0.3 microangular seconds, the distortion calibration accuracy can reach 0.28 microangular seconds, which meets the distortion calibration requirements of nearest neighbor habitable planet exploration.