As an important part of space information network, low-orbit satellite Internet of Things (IoT) has the problem of high complexity of interference calculation in interference analysis and coordination with other communication systems due to its proliferation of constellation size, dynamic satellite platform and large number of terminals. In addition, the distribution of IoT terminals in practice is highly correlated with geography and population, but due to the large coverage area of a single satellite, it will face multiple densities and deployments of terminals, and the use of static traversal calculations will bring an explosion of computing power. Starting from the mechanism of co-channel interference generation, the regionalized transmit field strength is used as the core of modeling the uplink aggregate interference of dense IoT terminals, and the Poisson Point Process(PPP) distribution model is introduced to equivalently model the ground terminals, so that the regionalized uplink aggregate interference is only related to the distribution parameters and transmit parameters, but not to the exact location and number of terminals. The simulation results show that the proposed method has less error compared with traditional link analysis, and has better fitting performance for different number of terminals. It can effectively reduce the computational complexity in long-time analysis, and can be used for interference analysis and calculation with high efficiency.