In this paper, the enabling technique of maintenance and reconfigurati on control of spacecraft formation flying is studied. First, the state transfer matrix of relative motion was introduced and the expression of relative motion with constant thrust control was educed. Then, 3 models of thrust were illustrated, which are impulse thrust, continuous thrust and Bang-Bang thrust. With the state transfer matrix, the differences of the thrust models in relative motion control were explored. Results show that in first order means the relative motion control effects with impulse thrust, continuous thrust and Bang-Bang thrust control are equivalent. So the problem of maintenance and reconfiguration of spacecraft formation flying could be implemented with Bang-Bang thrust control.