Series Micro Gear Flow Meter belongs to a kind of volumetric flow meter can be used for measuring volume and flow precisely. The flowing fluids makes the gear inside engage and rotate. Under the flowing effect of fluids, the pressure difference is formed between the inlet and outlet of the instrument. One pairs of gears can rotate freely without the need of power supply. The empty cavity between gears is filled with liquids, which is discharged through rotation. The liquid flowing through instrument and liquid flow can be known through measuring the number of revolutions of gear.