A fuel injection system for marine engine is studied in this paper. A hydraulic pump is driven by an electric motor and a cylinder motion is controlled by the pump flow rate. The cylinder piston pushes a plunger pump and fuel is pressured. The fuel injection system is controlled by the electric signal. This paper, simulation study is carried out using a model of the DDVC system. Simulated results are compared with experimental results. It has been shown that the simulation model good enough to predict the dynamic characteristics of the DDVC system.