A novel catalyst for the Fenton reaction was prepared by immobilizing Fe(III) onto collagen fiber, and its catalytic activity for the photoassisted decomposition of Orange 11 was investigated. The results indicated that this catalyst, Fe(III)-immobilized collagen fiber (FICF), follows an adsorption-decomposition mechanism so that it can effectively accelerate the decoloration and mineralization rates of Orange U in aqueous solution. Catalyzed by FICF (0.5 g/L, 91 mg/g Fe loading), the TOC of Orange 11 solution (1000 mL, 0.2 mM, pH 6.42) was 62.9% removed within 90 min under UVC irradiation (254 nm, 10 W) in the presence of H,02 (5.0 mM); meanwhile, the dye solution was completely decolorized. FICF can be recycled 10 times with little activity loss, and its catalytic activity can be easily recovered by reimmobilization of Fe(III). Therefore, FICF could act as an efficient and cost-effective catalyst for the photoassisted decomposition of Orange II.