Abstract: In the present paper, the effect of rolling motion on two-phase frictional pressure drop in rectangular channel was studied experimentally and theoretically. The result showed that, under rolling motion, the frictional pressure drop fluctuated similar to sine movement. And the frequency of the fluctuation was the same as the rolling frequency. Time averaged two-phase frictional pressure drop didn’t vary with rolling motion. The relative fluctuant friction pressure drop decreased with Full Liquid Reynolds number and mass quality increasing, and increased with rolling amplitude and rolling frequency increasing. The result also showed that, the relative fluctuant friction pressure drop did not vary with maximal angular acceleration. An empirical correlation to predict the relative fluctuant friction pressure drop under rolling motion was got.