Quantum-noise randomized cipher(QNRC) is a kind of physical-layer encryption technology based on Heisenberg uncertainty principle, which can be applied to high-speed, large capacity and long-haul optical fiber communication network. In order to solve theproblem that the modulation and demodulation of M-ary Y-00 ciphertext signal in QNRC system is limited by ADC chip with high sampling rate and high conversion depth, a method to modulate and demodulate Y-00 ciphertext signal is proposed by using multiplephase modulators(PMs) in series, and the performances of the proposed scheme are verified by using VPItransmission Maker Optical Systems simulation software. The simulation results show that based on the series structure of multiple PMs, a phase shift keying- quantum noise random encryption(PSK-QNRC) system with 126 ciphertext states, 10 Gbit/s data rate over 1000 km optically amplified links is realized. And it is also shown that reducing the mesoscopic power of the ciphertext quantum state can improve the security level of QNRC system, but it will damage the transmission performance of the system at the same time. Therefore, it is very important to select the appropriate mesoscopic power to optimize the security and reliability of QNRC system.