Abstract: In view of the uncertainty of thrust acceleration, enormous error occurs in tracking and navigating maneuvering target during orbit transfer process. In this paper, three components of position and velocity with respect to ECI coordinate system are augmented with thrust acceleration to be augmented system states, whose dynamical equations and measure equations are developed in ECI frame, and a minimum variance filter for estimation of augmented system states is presented, and the issues on linearizing non linear augmented state equations are discussed in detail. Simulation results are employed to illustrate that the algorithm developed here can track and position maneuvering target in real time during orbit transfer process.