Abstract: An experimental study about the effect of solenoid valve drive current on fuel injection characteristics was carried out on an electronic unit pump(EUP) test bench. Firstly, the delay relationships among all parameters of EUP fuel injection system were investigated, including control signal from the ECU, drive current, pressure at high-pressure pipe, injection rates and needle lift. Then, variations of injection volume with the change of holding and opening current were explored. The experimental results show that different opening and holding current has great influence on fuel injection characteristics and it also results in the parameters' variation of fuel injection system with certain regularity, including injection rate, injection pressure, needle lift and injection volume. Consequently, to minimize the influence on the fuel injection characteristics, it is needed to search the optimal opening and holding current respectively for different solenoid valves.