Abstract: The liquid slug region of slug flow affected by the wake of Taylor bubble, the hydraulic characteristic parameters of slug flow have different characteristics in different regions alone the flow direction. In this paper, the distribution characteristics of local parameters in slug flow in a vertical narrow rectangular channel were studied. The results show that the radial force of the bubble near the wall is relatively balanced and the frequency of bubbles near the wall is larger. The frequency of bubble in the middle of pipe increases gradually as it moves away from the Taylor bubble wake. According to the fluctuation of bubble frequency, the liquid slug region can be divided into three regions: The wake region accounts for 40% to 45% of the length of the liquid slug region, the transition region accounts for 10% to 15%, and main liquid region accounts for 40% to 50%. Since the wake region accounts for large, its influence cannot be neglected. The void fraction presents a “three-peak” distribution in the wake region and the main liquid region. With the increase of gas velocity, the peak value near the wall in the wake region gradually increases, and the peak value in the middle of the pipeline gradually decreases, but the situation is opposite in the main liquid region. The bubble diameter increases with the gas velocity, and the phenomenon of bubble coalescence and breakup in liquid slug region is less.