Abstract: A novel type of 3 radiation ionization gas flowmeter is introduced based on the molecule-marked method measuring the air stream velocity. The faint current from a ionization room is detected to a computer through an A/D converter after being magnified and filtered by an analogue-signal-processing circuit. Through a peak-seeking software, the flow rate can be achieved by the non-touching method even under bad conditions. The detailed design of hardware and software is given.