Abstract: The visualization method was used to investigate the parameters of slug flow unit in rectangular channel （40 mm×3 mm） under vertical and inclined conditions, aiming at establishing the pressure model of slug flow in rectangular channel in rolling motion. The calculation correlations for void fraction and two-phase velocity for gas slug segment were acquired, and the applicability of drift flux model was confirmed for liquid slug segment. The length fraction and void fraction of slug flow unit were calculated. According to the experiment results, the pressure model of slug flow model was established, and the predicted frictional pressure drop turned out to be in a good agreement with the experiment value.