The demonstrator is a biology teaching aid for demonstrating the blood circulating. It depends on a heart-action simulating micropump provided for both liquid and gas to maintain the pressure difference between liquid channel and low pressure chamber, and through both gas-and liquid-pipe injects air into foaming liquid to form a liquid fluid with air bubbles flowing in transparant pipe to demonstrate the blood circulating and recovers automatically the foaming liquid, and adopts the light-obstructing trap method to demonstrate the heart constriction. The flow direction of the liquid fluid indicating in the transparant pipe is strictly in keeping with the blood circulating direction by means of the transparant membrane obstructing hidden tube throttling method. The demonstrator is mainly made up of plastics the primary technology of production is the plastic moulding and bonding.