Lower engine emissions like CO2, particulate matter (PM) and NOx have recently become more necessary in automobile engines to protect the earth’s environment. Keeping uniformity of air/fuel mixture and decreasing fuel adhesion on walls of cylinder and piston are effective in order to reduce the engine emissions. In order to achieve the target fuel-spray, fuel injectors for gasoline direct injection engines need to be designed to deal with multiple injections. One of difficulties in the multiple injections is to control fuel spray behaviors during opening and closing valve; flow rate and spray penetration which are changed due to slow velocity of fluid during opening and closing valve, cause non-uniformity of air/fuel mixture that results in increase of PM. In this study, we developed an air/fuel mixture simulation that is connected with an inner-flow simulation with a valve opening and closing function. The simulation results were validated by comparing the simulated fuel breakup near the nozzle outlets and the air/fuel mixtures in the air region with the measured ones, revealing good agreement between them. It was found that the opening and closing of the valve affected the front and rear behaviors of the air/fuel mixture and also affected spray penetrations. It was also found that the magnetic circuit with the solenoid needs to be designed to achieve high speed valve-motion, and also keeps same valve motion in each injection, especially during opening and closing valve.