Abstract: Inter-cell co-interference caused by side lobes of satellite multi-beam antenna is an important basis for network planning and engineering design of satellite communicate system. Aiming at the interference problem caused by the side lobes of multi-beam antennas, firstly, based on the analysis of system frequency planning and downlink co-channel interference generation mechanism, the downlink co-channel interference model of multi-beam satellite communication system is obtained. Secondly, the satellite single beam antenna model is designed according to the antenna radiation characteristics given in Recommendation ITU-R S.672-4. Then, according signal beam antenna model and the requirements of the multi-beam antenna covering the ground, the coverage parameters of multi-beam antenna are obtained through geometric analysis. Finally, using the OPNET network simulation software, the satellite single beam antenna is modeled by the ema programming mechanism, and in a rectangular area of 80° east and west longitude and 64.8°north and south latitude, radiation characteristics of multi-beam antennas and downlink co-channel interference characteristics of 7-cell co-frequency and 3-color multiplexing are obtained through the mobile statistic of 109 mobile data receivers located at 1.2° apart on the same meridian. The simulation results show that the proposed model can accurately calculate the carrier interference ratio of any latitude and longitude under satellite multi-beam antenna coverage and carrier interference noise ratio intensity map of the whole network.