The liquid-liquid extraction is a basic and important unit operation for process industry. A lot of studyindicated that drop formation plays an important role in extraction because of 10-50％ of mass transfer occurringin this stage. Till now，little attention was concentrated at the interface instability induced by mass transfer（the Marangoni effect) during the drop formation. In this work，experiments were carried out with different flow ratesand drop concentrations to find how drop formation time，concentration and Marangoni effect affected the masstransfer coefficient during drop formation. The experimental results without the Marangoni effect were found toagree well with the numerical predictions of drop surface area and mass transfer rate. When the concentration driving force reached the critical value，the Marangoni effect would occur. The higher the solute concentration，themore intensive the Marangoni effect is. So the deviation of experimental mass transfer rate from the prediction based on surface stretch and fresh surface model increases with the driving force of mass transfer. The masstransfer coefficient was increased enormously because of the Marangoni effect and the flow rate for drop formation. The experimental results proved that the Marangoni effect had an important impact on the masstransfer during drop formation.