Flow-induced noise is an important source of gas water heater noise, and then it is of great significance to reveal flow-induced noise mechanism for noise reduction. Based on the experimental and numerical methods, this paper found that the acoustic radiation of pipeline system is mainly reflected in the vicinity of the fin of the water heater; however, it is pointed out that the excitation source of fin flow-induced noise is throttle valve. In this paper, a high-precision CFD and CAA joint simulation method is established, and the reliability of the joint simulation method is verified by experiments. Based on the numerical method, the flow-induced noise mechanism of the water heater flow was deeply revealed, and the key factors influencing the noise caused by throttle valve were obtained in order to provide reference for noise reduction.