Chitosan fiber for functional textile applications has drawn great attention due to its naturally occurring antibacterial activity, moisture-retaining and no allergenic reaction. However chitosan fiber has the weight loss defect under acidic processing conditions and during peroxide bleaching, which restricts its application and decreases its functionalities. In the present work, chitosan fiber was crosslinked by a water-soluble diepoxy compound with the aim of enhancing its acid resistance. The effects of crosslinking conditions (sodium carbonate dosage, crosslinker dosage and temperature) on the weight loss of crosslinked chitosan fiber in acid solution were studied. Additionally, the effects of crosslinking on the structures, resistance to peroxide bleaching, tensile strength, thermal stability and dye adsorption properties of chitosan fiber were also discussed. The results showed that the crosslinking by the diepoxy crosslinker was able to greatly reduce the weight loss of chitosan fiber in acid solution, and slightly reduce the weight loss during hydrogen peroxide bleaching. Crosslinking treatment slightly improved the thermal stability of chitosan fiber, and had no impact on the crystalline structure and dye adsorptions of chitosan fiber. However, the dry tensile strength of chitosan fiber decreased linearly with increasing diepoxy crosslinker dosage. (C) 2016 Elsevier B.V. All rights reserved.