Abstract: In the case of cognitive radio non-orthogonal multiple access (CR-NOMA) networks in dense cells, this paper proposes a combined user dynamic power allocation algorithm based on energy efficiency to address the problem of low channel band utilization when users adopt Underlay multiplexing. Under the premise of ensuring the quality of service of the primary user, the algorithm optimizes the combined multi-user access scheme based on the interference between users and the signal to interference plus noise ratio, maximizes the number of channel access users and improves the frequency band utilization. At the same time, the remaining power redistribution scheme is improved according to the power balance ratio under the gain sorting, making the reuse of idle power more reasonable and effective. The simulation results show that the proposed algorithm can effectively maximize the number of access users while improving the spectrum utilization