When the fluid flows through the probe, a high-pressure distribution area is generated in front of it, and the pressure of the high-pressure distribution area is slightly higher than the static pressure of the pipeline. According to the principle of Bernoulli’s equation, when the fluid flows through the probe, the speed increases, and a low-pressure distribution area is generated at the back of the probe. The pressure of the low-pressure distribution area is slightly lower than the static pressure of the pipeline. The flow of fluid past the probe creates a partial vacuum behind the probe and vortices on the sides of the probe. The cross-sectional shape, surface roughness and the location of the low-pressure pressure-taking hole of the average velocity flow probe are the key factors that determine the performance of the probe. The stability and accuracy of the low-voltage signal play a decisive role in the accuracy and performance of the uniform velocity probe. The flow probe can accurately detect the average differential pressure produced by the average velocity of the fluid. The flow probe has multiple pairs of pressure taking holes arranged according to certain criteria in the high and low pressure areas, making it possible to accurately measure the average flow rate.