A schematic manned lunar mission case based on coplanar lunar orbit rendezvous is investigated. Based on the principle of splitting the crew and cargo, the flight case including 3 launches and 2 rendezvous is designed. The launch window meeting the restriction of coplanar rendezvous and the characteristics of trans-lunar trajectory is obtained by precise dynamics model. Finally, the 3 missions of flight are arranged and the scale is estimated. The result from simulation shows that the TOF(time of flight) and energy of this mission case are feasible.