In this paper, the physical layer security of quantum-noise randomized cipher (QNRC) system based on quadrature phase shift keying (QPSK) is analyzed quantitatively with the secrecy capacity as the evaluation index. The key and data eavesdropping channel models are established, respectively. The expressions of key system and data secrecy capacity are derived, and the maximum security rate of the system is obtained. The effects of key parameters (scale number, internal optical amplifier gain and mesoscopic coherent state power) on the key and data security of QPSK-QNRC system are evaluated and compared with phase shift keying (PSK)-QNRC system in the same frame. The results show that the key system parameters have the same effect on the security of the two systems. Compared with the PSK-QNRC system, the QPSK-QNRC system has higher key security and maximum achievable security rate, lower data security, and stronger mesoscopic power level. At the same time, the maximum achievable security rate of the PSK-QNRC system is mainly limited by the security of key, while the maximum achievable security rate of the QPSK-QNRC system is mainly limited by the security of data.