Abstract: A maintenance control strategy for formation spacecraft flying in a near-circular orbit with fixed along-track distance tolerance was presented.By using the classical orbit element differences method,the periodic characteristics of relative motion and the influence of atmospheric drag on relative motion were analyzed.Using the relative drifts of along-track motion caused by atmosphere drag,the initial semi-major axis difference and the expected semi-major axis differences at the bounds of along-track tolerance box for the long time formation maintenance were designed.Afterwards,the along-track maintenance impulsive delta-velocities implemented at the bounds were given.Numerical simulation results indicate that the formation maintenance control strategy is feasible and requires fewer times of impulse and less velocity increment.Furthermore,the control algorithm is simple to be implemented autonomously by spacecraft.