Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it is more difficult to use them in a continuous process. Herein, we develop an enzyme immobilization technique for flexible tubing surfaces, which can be used to catalyze biochemical reactions in a continuous process. In this technique, the tubing is first treated with (3-aminopropyl)triethoxysilane at 50 degrees C and baked at 100 degrees C in vacuum to form a network of reactive amine functional group on the inner tubing surface. Subsequently, dextran polyaldehyde, a polymeric cross-linker, is used to immobilize crude protease extract and catalase for hydrolyzing casein and degrading H2O2, respectively, in a continuous process. The immobilized proteases are highly stable even after a long-term storage at 4 degrees C. After 12 weeks of storage, 90% of the original protease activity can be preserved. Meanwhile, the immobilized catalase is able to degrade 0.1% H2O2 solution flowing at 5 mu L/min. The immobilization technique is potentially useful for bioassays and industrial wastewater treatments when continuous processes are preferred.