In　order　to　know　the　mass　transfer　of　an　extraction　system,　the　mass　transfer　behavior　in　the　system　of　sec-butyl-acetate-acetic　acid-water　was　studied.　Firstly,　the　shadowgraph　optical　technique　was　used　to　observe　Marangoni　convection.　It　was　found　that　the　interfacial　cellular　convection　appeared　when　acetic　acid　concentration　in　aqueous　solution　reached　4.33　mol·L-1.　Secondly,　the　single　drop　method　was　used　to　determine　mass　transfer　coefficient　while　solute　acetic　acid　transferring　from　aqueous　solution　to　drops　of　sec-butyl　acetate　under　various　conditions.　The　effects　of　drop　formation,　acceleration　and　coalescence　on　the　measurement　of　single　drop　mass　transfer　were　considered　as　total　terminal　effect　in　the　experiment.　The　results　showed　that　overall　dispersed　phase　mass　transfer　coefficient　remarkably　increased　with　increasing　drop　diameter　and　experimental　temperature,　but　decreased　with　increasing　solute　concentration　in　continuous　phase.　Finally,　the　experiment　data　were　fitted　with　the　modified　combined　film　mass　transfer　coefficient　model.　This　study　is　important　to　the　design　and　scale-up　of　extraction　column.　©　All　Rights　Reserved.