An experimental and theoretical investigation on slug velocity measurement method in horizontal pipe was conducted.By analysis of the differential pressure signal

the low to high leading edge in differential pressure signal curve was found to correspond to liquid slug’s arriving at the upstream location of differential pressure transducer and the high to low leading edge correspond to liquid slug’s leaving from the downstream location of differential pressure transducer.The pulse width of differential pressure signal was the time in which a liquid slug moved from upstream location to downstream location of pressure transducer

and the product of slug velocity and pulse width was the sum of slug length and the distance of between two differential pressure transducers.By analysis of correlation velocity

it was found that the result obtained from conductance probe signal was the average of the slug velocity and interface wave velocity in liquid film section

the result obtained from differential pressure was the slug velocity and the result obtained from pressure signal was random.A good agreement was obtained between the experimental data of air-water

air-diesel oil

air-lubricating oil and the data of other authors.