To deal with the problem that the iteration doesn′t converge well in the maximum principle, a virtual satellite method is proposed to compute a fuel optimal trajectory of Mars probe in the processing of near-center braking. In the virtual satellite method, an optimal trajectory is computed in which the real satellite rendezvous with the virtual satellite so that the real satellite will come into the target orbit. The problem of guessing initial value of co-states is solved by transfer the original co-states, which have no physical meaning, into another one that can be guessed easily and by this way the iteration will converges better. Finally the simulation results prove the efficiency of this method.