A new immobilization strategy of catalases on natural fibers was reported in this paper. Catalase (CAT) from Bacillus subtilis was assembled into multiple layers together with poly(diallyldimethylammonium chloride) (PDDA) on wool fabrics via layer-by-layer (LBL) electrostatic self-assembly deposition. The mechanism and structural evaluation of LBL electrostatic self-assembly were studied in terms of scanning electron microscopy (SEM), surface zeta potential, and apparent color depth (K/S). The SEM pictures showed obvious deposits absorbed on the wool surfaces after LBL self-assembly. The surface zeta potential and dyeing depth of CAT/PDDA-assembled wool fabrics presented a regular layer-by-layer alternating trend along with the change of deposited materials, revealing the multilayer structure of the wool fiber immobilized catalases. The V (max) values were found to be 2,500 +/- 238 U/mg protein for the free catalase and 1,000 +/- 102 U/mg protein for the immobilized catalase. The K (m) value of free catalase (11.25 +/- 2.3 mM) was found to be lower than that of the immobilized catalase (222.2 +/- 36.5 mM). The immobilized catalase remained high enzymatic activity and showed a measureable amount of reusability, which proved that LBL electrostatic self-assembly deposition is a promising approach to immobilize catalases.