Summary As the core technology of mobile communication system, multiple access technology directly determines the performance and capacity of the system. However, with the rapid growth of the number of mobile communication system users and the high rate service demand, these orthogonal multiple access technologies are limited by the spectrum efficiency and access capacity, so it is difficult to meet the future mobile communication demand. Therefore, for the fifth generation mobile communication system (5G), the research of non‐orthogonal multiple access (NOMA) technology to effectively improve the system capacity has been widely concerned. The purpose of this paper is to analyze the influence of interference and power distribution on system performance simulation based on the simulation results of two most representative NOMA technologies, sparse code division multiple access (SCMA) and NOMA. This paper firstly briefly analyzes the SCMA system model and key technologies and, on this basis, introduces the SCMA system simulation platform, including basic platform parameters and platform simulation flow chart. Furthermore, the influence of adaptive modulation coding on the performance improvement of SCMA system is analyzed by simulation. Then, based on the NOMA system model, this paper carried out the research on fairness among NOMA users. Based on Lagrange multiplier method, this paper simulates fairness under the restriction of power allocation optimization algorithm, the number of users in different area, different radius and different transmission power, the village of village fair index, the change of the frequency spectrum efficiency and energy efficiency curve, the throughput rate between 0.8 and 1.4 changes, and the conclusion that has a guiding significance for NOMA system design.