Abstract: The paper introduces the building of the flowmeter of the artificial heart and lungmachine (also called the extracorporal circulation machine) by using a single-chip micro-computer and an photo-electronic transmitter. The apparatus can collect accurately therotation velocity of the pump fixed in the artificial heart and lung machine. It can com-pute accurately the blood flow needed by patients of different weights and surfaces ofthe skin so that we can control the flow of blood and ensure the heart operation is con-ducted successfully. It has changed the backward state of manual calculation whileoperation is going on. The flowmeter is a new intelligence meter.