Natural lac dye was applied to the dyeing of chitosan fiber in order to prepare healthy and hygienic textile materials, and the adsorption and functional properties of lac dye on chitosan fiber were studied. The functional properties of the dyed chitosan fiber depended greatly on the adsorption quantity of lac dye, which was related to dyeing temperature, neutral electrolyte dosage, and initial dye concentration. Lac dye displayed a very high adsorption capability on chitosan fiber, and a high utilization rate. The research on equilibrium adsorption showed that the Langmuir-Nernst isotherm was the most appropriate model to describe the behavior of lac dye, and the electrostatic interactions between lac dye and chitosan fiber contributed to Langmuir adsorption whereas the non-electrostatic interactions contributed to partition adsorption. The functionality analyses showed that the dyed chitosan fiber exhibited the good antioxidant activities determined by the DPPH radical scavenging assay and the ABTS radical decolorization assay, and the good deodorizing performance towards ammonia. This study points out that the lac dyed chitosan fiber can be utilized as functional textile materials with the requirements of antioxidant activity and deodorizing performance. (C) 2013 Elsevier Ltd. All rights reserved.