Abstract: An approach to some characterishcs of moonward trajectories stated from circular parking orbit and lunar orbits by a patched conic technique is presented in this paper. If the earth-moon transfer traectory is coplanar with the Moon's orbit, the reahonships between selenocentric orbital paramcters and the injection conditions of transfer trajectories can be described by a set of algebraic equations; if not, by a set of simultaneous transcendental equahons which can be solved by an iterahve technique. Some conclusion are obtained by numrical simulations.