Abstract: The computational amount of the existing power allocation scheme to maximize energy efficiency for uplink non-orthogonal multiple access (NOMA) systems needs to be reduced. To solve this problem, low complexity power allocation scheme to maximize the energy efficiency is proposed for uplink NOMA system. Firstly, the minimum power required by each user is calculated according to the minimum rate requirement of the users, the power allocation optimization problem for maximizing energy efficiency is established with the constraints of the maximum transmission power and the minimum rate requirement of the users. Then, maximum energy efficiency and its corresponding power allocation are obtained with the powers of all users as a constant. Finally, the solution of power allocation to maximize energy efficiency is solved with variable total power. Simulation results show that the energy efficiency of the proposed scheme is higher than or equal to that of the existing schemes in the same scene with the change of signal-to-noise ratio.