Abstract: Based on VOF model,the Taylor bubble and its surrounding characteristics of flow field are analyzed in a vertical rectangular narrow channel at different liquid flow rate.It shows that the relationship between the dimensionless bubble velocity and capillary number agrees well with those experimental results in cubic channels reported in literature The wall stress distribution around a gas slug has been investigated and the results show that the wall stress increases from the bubble nose to tail,but severe random motion would be occurred at the region behind the bubble tail.Meanwhile,as liquid flow rate increases,the Taylor bubble shape becomes much sharper and the liquid film thickness becomes thicker gradually,however,both the wall stress and the liquid axial velocity decrease and thus the portion of downward flow becomes shorter.