The attitude-orbit coupling effect of low-thrust maneuvering flight of spacecraft in medium or high orbits is relatively obvious, which brings some difficulties to the real-time reconstruction and calculation of the flight trajectory. At the same time, the error of exterior trajectory measurement data has a significant impact on the flight trajectory accuracy in the medium or high orbits. To solve these problems, an unscented Kalman filter algorithm for dynamic modeling is proposed. The state model, observation model, and implementation process of the algorithm are given also. The application effect of the algorithm is calculated and analyzed through some real measured data of a low-thrust maneuver. The calculation results show that the algorithm can adapt to the low-thrust orbit changing process in the medium or high orbits. The research results have some reference value for the flight trajectory reconstruction of spacecrafts in medium or high orbits.