Abstract: The emerging fleet of non geo-stationary orbit (NGSO) satellite constellations are able to connect a large number of terminals all around the world. Moreover, NGSO constellation system has high dynamic characteristics in the domains of space, time, frequency, and coding, etc. Most NGSO satellite systems use the same frequency band as geo-stationary orbit (GSO) constellation systems. Therefore, it is inevitable to bring time-varying interference to GSO satellite systems in the sharing frequency bands. The problem of how to generate the maximum uplink radiated power of NGSO constellation is solved in this paper. The generation method of the equivalent is equivalent isotropically radiated power (EIRP) mask in the uplink of NGSO satellite constellation system is improved by introducing the latitude range of non-GSO earth stations, the visible GSO arc, the minimum separation angle at the earth stations, the earth stations directional antenna gain. A simulation example is shown in this paper. Through simulation analysis, it can be known that the more detailed operating parameters of the working system to be got, especially the related avoidance strategies and mitigation techniques, the more accurate results can be simulated, which is closer to the true value of the NGSO constellation system. The proposed method can be used to calculate the EIRP mask in order to participate in the uplink equivalent power flux density (EPFD) calculation in article 22 of ITU Radio Regulations.