Abstract: The gas-liquid two-phase pulsatile flow was studied in a rectangular channel with 40 mm×3 mm cross section under different periods, flow rate amplitudes and its mean values (mean Re_l<10 000, mean Re_g<800). There was difference between the single phase pulsatile flow and the gas-liquid two-phase pulsatile flow, and pulsation period and amplitude were not sensitive for the average frictional pressure drop. There was no significant difference on the values and distribution between the calculation deviations in pulsatile flow and the calculation deviations in steady flow by using different empirical formulas. Almost all of the relative deviations were less than 20%, and the relative deviations of Mishima-Hibiki method and Lee-Lee method were less than 10%. The results show that the empirical formulas for the two-phase steady flow frictional pressure drop are also suitable for the calculation of the average value of two-phase pulsatile flow.