The control valve is the most important implementation part of a high pressure common rail system, and its flow characteristics have a great influence on the performance of an injector. In this paper, based on the structure and the working principle of an electromagnetic injector in a high pressure common rail system, a simulation model of the injector is established by AMESim software. Some key parameters of the control valve, including the volume of the control chamber, the diameter of the orifice Z (feeding orifice), the diameter of the orifice A (discharge orifice) and the hole diameter of the fuel diffusion hole are studied by using this model. The results show that these key structural parameters of the control valve have a great influence on the establishment of the control chamber pressure and the action of the needle valve. Within a certain range, when the control chamber volume is small, the control chamber pressure changes rapidly, the needle moves quickly, the system reacts quickly; increasing the diameter of the orifice Z (feeding orifice) facilitates the closing speed of the needle valve but reduces the opening speed of the needle valve; increasing the diameter of the orifice A (discharge orifice), the valve opening speed accelerates, closing delay time unchanged; increasing the diameter of the fuel diffusion hole, the needle closing time increases, the fueling duration time is prolonged and the fuel injection quantity increases. On the basis of this, the cavitation problem at the sealing seat of the control valve sleeve in the common rail injector is simulated by CFD simulation, and the process of cavitation is deduced. In the existing structure, it is possible to reduce the cavitation phenomenon by increasing the length of the fuel diffusion hole of the control valve.