The high sampling rate and high resolution digital-to-analog converter(DAC) is one of the core components to improve the performance of quantum noise random encryption(QNRC) system, which has been restricting the development of QNRC system technology. In order to explore the effects of different DAC sampling rates and resolutions on the performance of the QNRC system, the VPItransmission Maker Optical System 9.1 software is used for system simulation design. Firstly, a QNRC ststem basded on phase-shift keying modulation with mesoscopic power of -21 dBm, transmission distance of 1000 km, transmission rate of 10 Gb/s and number of ciphertext states of 28-1 is built. Then, the sampling rate and resolution of DAC are changed to compare and analyze the performance of QNRC system. The analysis results show that when the DAC sampling rate and resolution are 30 Gb/s and 6 bit respectively, the QNRC system has the best cost-performance ratio.