The halo orbit with specific amplitude and direction around Earth-Moon L2 libration point is the nominal mission orbit of Chang’e 4 relay satellite “Queqiao”. Beyond the mission orbit， relay satellite could be captured to other orbits around Earth-Moon L2 libration point and could continue supplying communication relay to the lander and rover on the far side of moon. Capture area intuitively and quantificationally show ability and scope of relay satellite captured around Earth-Moon L2 libration point. Capture area of Earth-Moon L2 libration point relay satellite is systematically investigated. Capture effects are analyzed in terms of lunar occultation， communication relay， orbit maintain control， etc. Quantitative analysis methods are designed for influence factors of Earth-Moon L2 libration point relay satellite mission. Our results are verified by simulation based on mission measured data. Research results show that， comparing with the mission orbit， other capture orbits have distinct communication relay effects. Effects on communication relay in capture area could be quantitatively distinguished based upon the calculation results. Analysis of capture area of Earth-Moon l2 libration point relay satellite is meaningful to supplying technical reserve and reference for orbit design in future relevant missions.