As one essential component of a pressurized system, a relief valve is used to guarantee the pressure within a prescribed range. But in practical engineering, pressure fluctuation caused by the operation of a relief valve will travel along the pipeline and couple with the motion of the valve, which might result in malfunction of the valve and the system. In order to investigate the fluid-structure interaction (FSI) phenomenon, a hybrid model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the hybrid FSI model, the characteristics of pressure resource is modeled using the performance curves, the compressible gas transmitting in the pipe is calculated by one-dimensional MOC, and the air flow in the valve as well as the valve motion is simulated by a two-dimensional CFD model. To validate the hybrid model, 1:1 scaled test rig is conducted. The compared results show that the hybrid model not only can accurately capture the pressure fluctuation in straight pipeline induced by the closure of the valve but also can accurately predict the forms of the valve motion.