Convenient and effective method is necessary for analyzing characteristics of flow passage correctly. However, in the characteristics analysis of fuel metering valve, the linear analysis theory is not useful because the system is nonlinear. In this paper, by way of applying Flow Gain Method (FGM), the nonlinear features of model were removed, the linear model of the valve is set by the method above and research is carried on a fuel metering valve. The result shows that the method simplifies the analysis process, resolves the difficulty of design and optimization of valve. At the same time, the linear model using Flow Gain Method compares with the nonlinear model simulation results, it shows that the method is effective.