Abstract: For the interruption of directcommunications with Mars duringsuperior conjunction, relay architecture based on the Sun-Earth Lagrange point L₄/L₅ for the relay to Mars was proposed. The mathematical model of the pointing vector from L₄/L₅ to Mars under the heliocentric ecliptic inertial coordinate was established at different spatial reference coordinates system transformation. The analytical expression of spatial characteristic parameter which was L₄/L₅ pointing to Mars along with the instantaneous orbital elements of celestial body was deduced. Simulation experiment shows the variation of spatial characteristic parameter in one tropical year between Earth and Mars. One sustained connection model which was viewed from L₄/L₅ to Mars surfaces was designed and the performance of the return link was analyzed. It provides a reference for the design of inter-satellite link of L₄/L₅ pointing to Mars.