The reaction field and rate-determining step of the transesterification of SLT allylester allyl (5 chloro-2-oxo-1,3-benzothiazol-3(2H)-yl) acetate with methanol to form SLT-methylester in dichloromethane using potassium carbonate (K2CO3) as a catalyst were investigated, The reaction rate in solid -liquid phase was 45 times higher than that in homogeneous liquid phase, which indicates that the reaction takes place almost exclusively on the surface of K2CO3 particles rind the reaction on the surface of K2CO3 is rate-determining step. In addition, by changing the order of supplying the reactants and catalyst into the reactor, it was found that the occurrence of an induction period for the reaction in the solid-liquid phase was caused by the combination of methanol with K2CO3.