Abstract:  The co-frequency interference analysis between NGSO（non-geostationary orbit）constellation systems usually used link-level interference evaluation indicators to judge harmful interference，but for constellation systems with multiple links，single-link-level indicators could not fully reflect the interference of the entire system.To solve this problem，a system-level capacity loss index was designed to evaluate the co-channel interference between constellation systems，and the probability distribution of capacity loss between hybrid configuration NGSO constellation systems was modeled and simulated.In the coexistence scenario of typical constellations，if the large constellations actively take interference avoidance measures based on space separation，the maximum system capacity loss would be reduced from 35% to 0. If small constellations take active interference avoidance measures，the maximum system capacity loss would deteriorate from 78% to 100%.The results show that，with the increase of the constellation scale，active avoidance measures can effectively mitigate the capacity loss caused by frequency interference；when the scale of constellation decreases，active avoidance measures will increase the risk of link interruption and cause system capacity deterioration.Finally，suggestions for interference avoidance strategies are proposed for constellations of different scales.

Key words: NGSO constellation, system-level interference evaluation criteria, co-frequency interference, NGSO coexistence, communication throughput