Abstract For improving the physical properties of old corrugated container (OCC) fiber, the laccase/histidine system was used in this paper. Firstly, the paper studied the optimum conditions that the laccase/histidine system modified the OCC fiber, including enzyme dosage, histidine dosage, reaction time, reaction temperature, and pH. Experimental results showed that the optimum reaction conditions of laccase/histidine system for OCC pulp were: dose of enzyme 1 U· g − 1 {\text{g}^{-1}} , 4 h reaction time, pH 4.5, dose of histidine 1 %. Under the optimum reaction conditions, the tensile and burst indexes of the sheet made from laccase/histidine treatment were increased by 25.2 % and 34.0 %, compared with that of the control sample. The SEM results showed that compared with the control sample, the fibrillation of the fiber modified with laccase/histidine was more obvious. Finally, the content of acid-insoluble lignin of the fiber was determined. The content of acid-insoluble lignin of the control sample was 29.2 %, and the content of acid-insoluble lignin of the fiber treated by laccase/histidine system in optimum reaction conditions was 16.0 %, which decreased by 13.2 %. Laccase/histidine system could improve the physical properties of recycled fiber, alleviate fiber decay, which are of great significance to solve the resource shortage and environment pollution of the paper-making industry.