Abstract: Aiming at the problem of co-frequency interference between non-geostationary orbit (NGSO) constellation system and geostationary orbit (GSO) satellite system, aggregated interference analysis model for NGSO multi-beam constellation system is established, and the dual step algorithm of spatial position probability is proposed for interference analysis simulation based on relevant ITU recommendations and reports. This method discretizes the spatial position of NGSO reference satellite by dividing the latitude and longitude grid. Then the probability density function of interference-to-noise ratio (I/N) can be obtained. Taking OneWeb and SINOSAT-5 system as the typical NGSO constellation system and GSO satellite system respectively, the interference analysis is performed by using the proposed method, and the results are verified with International common tool. The results illustrate that when the threshold of the number of NGSO satellites whose separation angle is not more than the included angle of the fine step size region is 20%, both the result accuracy and calculation efficiency can be balanced. The I/N distribution is related to the latitude of the ground station.