Through the combination of numerical simulation of computational fluid dynamics and model test, the relevant research on the mechanism and function that the environmental protection valve of trailing suction hopper dredger reduces the air entering the overflow cylinder are conducted. The model test and numerical simulation results are compared to verify the accuracy of gas liquid two phase flow numerical model. The calculation of different inlet flow rates and different environmental protection valve angles is made to obtain the mathematical description of correlation among inlet flow rate, hopper liquid level, and environmental protection valve angle, and according to such a description, the control strategy of environmental protection valve is established. The numerical model of stacked overflow cylinder is established and its effect on reducing the overflow is analyzed.