The Fluid flow in the gating systems of propeller casting with the aid of transparent models made of plastics, in which the flow of metal is simulated by that of water, is studied. The effect of sprue base and 2nd sprue on the rate and the quality of the flow, viz. whether the flow is quiet or agitated, whether entrainment of air bubbles occurs, is mainly discussed. It was summarized that the design of sprue base was important to avoid the intense agitation of the flow and the considerable aspiration, and the use of 2nd sprue was effective in decreasing the rate of flow and in washing away the trapped air.