A cone throttlingpart is hung in the pipeline center of BF30 V-cone flow meter. The conethrottling part rectifies the current curve and forms immediately the lowpressure region in cone's downstream. There is a differential pressure between thepositive pressure from the pipeline upstream and the negative pressure which remainsafter passing through. The differential pressure takes out the positive and negativepressure with the mouth of pressure getting (the positive pressure mouthlocated at pipeline's upstream, the negative pressure mouth located at cone'sterminal). By measuring the differential pressure between the two mouths ofpressure getting, we can calculate the flow according to the Bonuli equation.The cone located at the pipeline center may carry on the optimization to the measuredmedium current curve , therefore the measuring accuracy is high, while the requestsis low to the measuring upstream and the downstream of the instrument of the straightpipe.