Abstract: Under the condition of high pressure difference, the throttling effect of flow control valve results in the problem of vibration and noise. In order to control the noise of the water injection system, this paper makes a low noise optimization design from the viewpoint of system configuration and proposes a noise reduction scheme for multistage throttling. The principle of low noise design is analyzed by numerical method of fluid dynamics, which verifies the effectiveness of the multilevel throttling scheme. Based on the principle of low noise design, three stage flow control valves in series are designed to control the flow in this paper. Then the paper numerically analyzes the flow field and sound field, and the analysis results indicate that the three stage throttling design makes the low pressure area smaller and the local cavitation reduced behind valves,,a large scale vortex structure appears at the lower edge of the inlet and the upper edge of the outlet of the first two stage valves.