During the optimal design of transfer trajectory to translunar libration point，the payload launch capacity of Lunar Relay Satellite can be improved greatly if the electric thrusters which have high specific impulse and low thrust can be used as main propulsion. The optimal design of low-thrust transfer trajectory is studied which makes use of the invariant manifolds of Earth-Moon system based on the hybrid method. GEO is the initial orbit and halo orbit around translunar libration point L2 is the aim orbit of the transfer trajectory. The simulation result shows that thruster direction control strategy which consumes the least propellant for transfer trajectory has been obtained. The result is of great important engineering meaning.