Abstract:  For earth-circumlunar laser communication，a simulation model of the dynamic characteristics of laser communication link was established.The communication link characteristics were analyzed.Due to the earth occlusion，the total visible time of Kashi Station-circumlunar laser terminal for direct link or rely link are increased by about 4.5% and 6.5% compared to the Argentina Station，respectively.For the circumlunar terminal，the range of its ortation mechanism is -180° to 180° azimuth and -19° to +89.7° elevation，with 18.2μrad point ahead angle.Based on simulation results，the effect of sunlight interference was summarized.The changes of SEP or SPE angle of the laser communication link are approximately periodic，reaching a minimum value every 15 days.In laser communication link，the typical Doppler frequency shift is ±1.28GHz for the wavelength of 1550nm and the change rate of the Doppler frequency shift is 1MHz/s，so the communication system should be selected to suit the rapid changing of Doppler frequency.Based on the analysis，the link budget and signal system of circumlunar to earth laser communication link were proposed.The results can provide a reference for the design of circumlunar to earth laser communication.

Key words: lunar earth laser communication, circumlunar orbit, visibility, point ahead angle, doppler frequency shift, link characteristics, sun-earth-probe angle