The imbalance of fuel delivery between the left and right wing tanks will affect the aircraft handling and even flight safety. Based on the fuel delivery control principles of a certain type of aircraft， the structure of the double oil surface controller is optimized and improved. The internal flow field of the double oil surface controller is simulated by ANSYS software. It is found that the control port pressure has a large impact on its performance. When the pressure is low， the fuel flows out from the bell valve of the oil surface controller in the form of “gushing out”， which is more stable； but when the pressure is high， the fuel flows out in the form of “spraying out”， and the fuel will follow the trend into the the float chamber， which can prompt the end of the fuel delivery process ahead of schedule and seriously reduce the structural performance. According to the fuel injection trajectory obtained by the simulation， a baffle is designed on the upper float rocker arm to stop the fuel from entering the float chamber， so that the double oil surface controller can effectively widen the height difference of the fuel level at the beginning and end of the fuel delivery within the entire envelope range. The test results show that the oil level difference brought by the optimized double oil surface controller is several times higher than that of the single oil surface controller， which efficiently solves the problem of oil delivery imbalance. The optimization design of the oil surface controller can be promoted for other airplanes.