A polyamide microcapsule containing bi-enzyme, beta-galactosidase (beta-Gal) and glucose oxidase (GOD), was prepared by interfacial polymerization. The average diameter of the microcapsule was evaluated to be 5 mu m. The bi-enzyme-containing microcapsule was immobilized with tetrathiafulvalene on a carbon electrode surface and was characterized by cyclic voltammetry. The oxidation current increased with the increase of the lactose concentration. It was concluded that beta-Gal and GOD retained their enzymatic activity in the microcapsule and reacted with lactose, and tetrathiafulvalene penetrated the polyamide membrane.