Abstract: An investigation on the phase distribution in air - water gas - liquid two - phase flow in a hor-(?)ontal circular channel was conducted by using the double - sensor resistivity probe. The typical time se-ries signal of the probe were presented. The variations of phase distribution with variations of gas and liquid volumetric fluxes were analyzed and the present data were compared with prior work data and existing models. It was found that there exists a more complex phase distribution pattern in horizontal flow system than in vertical flow. The radial local void fraction profiles have a similarity at the same measuring angle with different gas and liquid flow rates. However, a non - symmetric profile can be observed at a given slice of pipe cross - section except along the horizontal axis of the pipe .