In this paper, we investigate improved spectrum concern by employing non-orthogonal multiple access (NOMA) scheme in cognitive radio (CR) network to form CR-NOMA and to serve many destination users. In secondary network of our proposed system, device-to-device (D2D) strategy is designed to support further transmission for NOMA users under impacts from interference from the primary network. Outage performance gap exists among these NOMA users since different power allocation factors assigned to the destinations. Unlike existing NOMA schemes as considering power allocation factors, which are not optimal in terms of outage performance, our proposed paradigm exhibits optimal outage in scenario of D2D transmission. In particular, the outage probability is first derived and approximate outage performance can be further achieved. Simulation results confirm exactness of the analytical expressions and show advantages of the proposed CR-NOMA system in terms of outage performance and throughput.