An up-link power from an earth station in a satellite communication system is controlled to compensate rain attenuation caused in an up-link so that the transmission power of the earth station is adjusted according to the difference between the level of a received reference signal, which is sent from a reference earth station to the satellite, and the level of its own received signal which is transmitted to the satellite from itself and is received at its own station after being relayed by the satellite. A transmission power of the reference earth station is adjusted so that the level of the received reference signal at the satellite is constant.