In order to explore the feasibility of modified cellulose as immobilization enzyme carrier, the extracted pineapple peel residue cellulose was uniformly modified with L-serine in ionic liquid and used to immobilize bromelain. The pineapple peel residue cellulose, modified pineapple peel residue cellulose and the immobilized enzyme were compared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analyzer and X-ray diffraction spectrum. The results showed that the pineapple peel residue cellulose was successfully modified, the crystal structure was changed from cellulose Ⅰ to cellulose Ⅱ. Bromelain was successfully immobilized on the modified pineapple peel residue cellulose, and the thermal stability of immobilized enzyme was higher than that of modified pineapple peel residue cellulose. The immobilization process and enzyme characteristics of the bromelain were studied. The results showed that the optimum preparation process of immobilized enzyme was that the mass ratio of pineapple peel residue cellulose to ionic liquid Cl was 3∶100, the mass ratio of L-serine to pineapple peel residue cellulose was 1∶1, the glutaraldehyde solution volume fraction was 1%, and the cross linking time was 1.0h. Compared with free bromelain, immobilized bromelain had better temperature stability and acid environment stability.