In this study, as a novel plastic garbage collector that collects floating fine plastic substances in the water, a jellyfish like robot system has been developed. On this system, unidirectional flow generated by opening and closing motion of umbrella makes jet flow pattern toward a jellyfish’s oral arm like garbage collector. This study focused on jet flow that influences on the garbage collecting performance. Through some experiments, we have found that the optimum open-close timing of umbrella at a range of high flow rate. Further it has been confirmed that the arm like collector of the jelly fish’s mouth can collect fine cellulose powder.