Ambient backscatter communication (AmBC) combined with non-orthogonal multiple access (NOMA) presents superior energy reusability and higher sum rate. However, existing studies failed to utilize the information of backscatter links. Therefore, to explore the impact of backscatter link, this paper employs three-user NOMA to improve the spectral efficiency. We propose a simple distance power allocation method to accomplish successive interference cancellation. Based on the Monte Carlo method, the outage probability of the proposal is analyzed. Our work provides a scheme for coexistence between AmBC and NOMA systems in the future Internet of Things.