Abstract: Taking three Walker constellation satellites which locate in different orbit as objects, the probability of a spacecraft approaching them without orbital maneuver is studied. The genetic algorithm is used to optimize the initial orbit which is obtained by Lambert method. The position and velocity's variation of the initial orbit on the reference time is encoded to form population. The minimum distance between the spacecraft and three constellation satellites is adopted as fitness function. The optimization result can be attained through the population's propagation. Finally, followed by the simulation, the performances of the least square method and the genetic algorithm are analyzed. At the same time, the orbital perturbation in the approaching process is taken into account. The genetic algorithm is suited for this problem of orbital optimization. The study results can be taken as the theoretical proof for a single spacecraft close approaching multiple constellation satellites without orbital maneuver.