The objective of this study is to experimentally investigate the effect of design parameter on the flow characteristics of a central-driven ejector. The design parameters are the primary nozzle area and distance ratios. The experimental setup is an open-loop continuous circulation system which has a movable nozzle ejector, an electric motor-pump, a water tank and a control panel. We calculated the mass ratio using the measured primary and suction flow rates with the experimental parameter of primary water flow rate or pressure. The results showed that the mass ratio increased with the primary nozzle distance ratio, while the mass ratio decreased with the primary nozzle area ratio.