Abstract: Chang'E-4 relay satellite,as an important part of Chang'E-4 mission,is different from other lunar probes. For the first time,it chooses Halo orbit around earth-moon L2 point to provide relay communication support for the lander and the rover on the lunar far side. There are many technical challenges have to be faced. Based on mission requirements and engineering constraints, the fault types related to orbit control in the whole life of the satellite are identified and three emergency control objectives are determined firstly, and then the emergency orbit control schemes are given in stages, and the lissajous orbit is proposed as an alternative mission orbit. Finally the propellant consumption, relay communication conditions and feasibility are analyzed finally. Research results have been applied directly to engineering practice.