Based on the analysis of the impact of perturbations on the absolute orbit of satellites, the spatial pipeline error will become increasingly large over time, so it is necessary to implement orbit control on the satellite to keep it within the preset orbit pipeline. This article introduces the composition of an orbit maintenance system for ultra-low orbit satellites and the implementation algorithm of autonomous orbit maintenance. The core of autonomous orbit maintenance is reference orbit optimization design, autonomous navigation, and autonomous orbit control strategy. Autonomous navigation mainly includes autonomous measurement of satellite orbit data, determination and prediction of orbit parameters. The autonomous measurement of orbit data is achieved using Global Navigation Satellite System (GNSS) receivers, which can provide real-time and accurate state vectors of the satellite in the ground fixed system. The determination of satellite autonomous orbit parameters based on GNSS measurement data adopts the method of filtering multi-point instantaneous roots to obtain the quasi average orbit elements. Real time filtering of GNSS measurement information through SR-UKF to obtain the orbital pseudoroot. The accuracy of autonomous orbit maintenance was simulated and verified, proving the correctness of the design.