This paper presents a noise channel model to analyses the channel characteristics between legitimate receiver and eavesdropper in quantum noise stream cipher system. The simulation results show that the channel advantage for legitimate receiver over eavesdropper can be formed by combining proper channel codes with quantum noise. Due to the fluctuation of the noise, the eye pattern degradation of the signals increased rapidly with the increasing of modulation order. In addition, the security gap in this paper is obtained by theoretical calculation. And with the increase of number of modulation order, the security gap increases significantly. After the number of modulation order goes beyond 32, the security gap is more than 0, when the number of modulation order goes up to 1024, the security gap is more than 12, which means the security and communication integration security and communication integration can be achieved.