Abstract: By separation of variables, the model equation of mass transfer of moving drops can be converted into two-variable Liouville equation. Calculus of variations and Ritz method are used to obtain eigenvalues λ2 and eigenfunctions BnZn(x, y) of the Liouville equation. The mass transfer coefficient F then can be obtained by linear superposition Experiments were carried out in a column of 76mm in diameter. Water and n-butanol were used as continuous phase and disperse phase respectively. Succinic acid as the solute was transferred from water to butanol drops. The model developed matched the experiment data quite well.