[en] The recent integration of backscatter communication (BC) with power-domain non-orthogonal multiple access (P-NOMA) has triggered significant research interest due to its applications in future sixth-generation (6G) wireless networks. However, the link security aspect of these networks has not been well investigated. This letter proposes a new optimization framework for improving the security of BC-enabled P-NOMA communication. Our system model takes into account the simultaneous operation of P-NOMA users and the backscatter tag (BT). Meanwhile, multiple non-colluding eavesdroppers (EDs) also try to target the signal of BT. Thus, the objective is to maximize the link security by finding the optimal reflection coefficient (RC) of the BT under the constraint of base station (BS) transmit power. Results demonstrate that the considered system with P-NOMA achieves high secrecy rate than the system using conventional orthogonal multiple access.