Influences　of　various　parameters　such　as　liquid　inlet　flow,　feeding　height,　inlet　aperture,　diameter　of　tube　and　inclined　angle　on　the　wetting　ability　of　liquid　film　were　studied.　Image　processing　method　was　adopted　to　measure　wetting　length　of　liquid　film　on　the　plain　tube　with　different　parameters.　The　experimental　results　showed　that　with　the　increase　of　the　flow　rate,　the　wetting　ability　of　the　liquid　film　stays　the　same　after　reaching　the　peak.　When　the　feeding　height　is　investigated,　the　flow　pattern　needs　to　be　considered.　The　effect　of　feeding　height　on　wetting　ability　is　negligible　with　the　flow　pattern　of　columnar　flow.　Wetting　ability　decreases　firstly　then　remains　unchanged　with　increasing　feeding　height　under　columnar-sheet　flow　regime.　Shortly　after　sheet　flow,　wetting　ability　reaches　saturation.　As　for　increasing　the　inlet　aperture,　the　flow　pattern　needs　to　be　considered.　Wetting　ability　increases　first　and　then　decreases　under　columnar　flow,　but　the　variation　is　relatively　small.　When　flow　pattern　is　transformed　into　columnar-sheet　flow　or　sheet　flow,　liquid　wetting　ability　will　fall.　Under　the　condition　of　a　certain　flow　rate,　the　larger　the　diameter　is,　the　larger　the　wetting　area　of　the　liquid　film　is,　but　the　worse　the　wetting　ability　is.　When　the　experimental　tube　is　not　horizontally　placed,　the　change　regulation　of　wetting　length　is　no　longer　symmetrical　with　the　liquid　inlet　column,　but　the　lower　part　is　stronger　and　the　upper　part　is　weaker.　©　2018,　Science　Press.　All　right　reserved.