Abstract: The frictional resistance characteristics of air-water mixture flow in two rectangular channels with different aspect ratios were studied under atmospheric condition. Prediction methods for conventional as well as micro- and mini-channels were verified and evaluated against the experimental data. It is shown that the corrections for conventional channels poorly predict the two-phase frictional resistance in narrow rectangular channel. The Lee-Lee correction fits well with the experimental data, but there still exists deviations in a certain parameter ranges. The modified correction of Chisholm C method based on Chen’s model was given by considering aspect ratio, all liquid Reynolds- number and L-M parameter, and it has a good agreement with the experimental data.