The bio reactors with high efficiency using ejector are widely used in gas-liquid system, This is also due to the high efficiency in gas dispersion resulting in high mass transfer rate and low power requirements. Thus, the new liquid fertilizer manufacturing equipment composed with aeration tank, cycling tank and circulation pump using an ejector was developed. The aim of this study is to investigate the effect of an ejector on the liquid fertilizer manufacturing equipment and to design the optimal ejector for actual application using CFD analysis and experimental method. The results show that the suction air mass flow rate is increased, as the diameter of driving ejector nozzle is smaller and the position of nozzle is toward the exit of an ejector.