A carrier containing primary amine groups was synthesized by the reaction between nitrilon fibre and diethylenetriamine, and papain was immobilized on this kind of carrier by using glutaraldehyde as a coupling agent. The factors involved with the activity recovery of the immobilized papain and the enzymic properties of the resulting immobilized papain were studied in comparison with free papain, for which casein was chosen as a substrate. The results show that the activity recovery of immobilized papain can reach 47.3%, and that the immobilized papain exhibits better environmental adaptability and reusability than free papain.