With the development of point-to-point fiber quantum key distribution technology and its commercial application, the multiplexing of quantum signal and classical data in the same fiber to improve system efficiency and save fiber resources has become one of the research hot issues in recent years. The source of noise is verified by the experiments based on two co-channel transmission schemes, and the influence of noise on the performance of quantum key distribution system is simulated and analyzed. In addition, the noise suppression schemes are evaluated and analyzed aiming at the existing problems in experiments, which provide experimental support for the commercial development of classical-quantum signals co-channel transmission. The experimental results show that the maximum security transmission distance in the co-propagating scheme without noise suppression at separate waveband is 75 km when the launched power is 0 dBm, while it can reach 164 kmat the same waveband by using narrow-band filtering. This work provides a feasible solution for noise suppression of co-channel transmission in future quantum-classical integrated optical networks.