Abstract: Experimental investigation and analysis of the pressure drop characteristic of flow boiling in narrow rectangular channel were conducted under rolling motion. Several correlations for the two-phase frictional pressure drop were evaluated against the experimental data. The results show that the correlations for conventional channel poorly predict the results. While the Zhang-Mishima and Sun-Mishima correlations developed for narrow channel are better than other correlations. On the other hand, the pressure drop characteristic of flow boiling was analyzed under rolling motion. The two-phase pressure drop changes cyclically due to the rolling motion, rolling angle and period almost have no effect on the fluctuation of pressure drop and the average two-phase frictional pressure drop.