Abstract: This paper introduces the working principle of the flow measurement system composed of wellbar flow sensor, differential pressure transmitter and flow totalizer. Wellbar flow sensor has special process shape, remarkable anti-blocking effect, small permanent pressure loss of pipeline, low installation cost and maintenance-free. It can measure the flow of full pipe and unidirectional fluid of various media such as gas, steam, fluid, etc. It is suitable for high temperature, high pressure, corrosive and explosion-proof dangerous places, with high precision and large range ratio.