Abstract: Through experiments which are done on DN25 water calibration equipment, the vortex flowmeter with trapezoid cylinder bluff body at low Reynolds number is investigated. The frequency of vortex shedding is calculated by digital signal process—spectrum analysis, which has better performance on linearity than analogue signal process and can detect lower limit of measurement. Reynolds number-meter factor K relationship is provided. It is found that the relationship of trapezoid cylinder bluff body decreases at low Reynolds num-ber which is different from the relationship of circular cylinder bluff body. And the meter factor K is driven to a constant when Re>2 000. Three reasons are analyzed and proposed: velocity profile in pipe, shape of bluff body and relationship between velocity and frequency.

Key words: Meter factor, Reynolds number, Vortex flowmeter