Abstract: Multisensor measurement fusion technology can improve the accuracy, reliability, and continuity when it is applied to parameters estimation. A new algorithm for orbit parameters estimation of formation flying satellites is proposed based on extend Kalman filter, and multisensor measurement fusion technology is also used. Derived from motion equation of absolute satellite orbit, the algorithm overcomes the localizations of Hill equation, in which many assumes are not met actually and is not suitable for the model with perturbations considered. Simulation results verify the feasibility and validity of the algorithm.