Chitosan extracted from shrimp shell and biochar derived from rice husk were used to synthesize chitosan-modified biochar. Adsorbent materials including biochar and chitosan-modified biochar were used to evaluate their adsorption capacity toward Safranin-O (SO) in aqueous solution, using batch adsorption experiment. Several parameters such as pH solution, material dosage, adsorption time, and initial SO concentration were studied. Results showed that, under the similar experimental conditions, the adsorption capacity of chitosan-modified biochar was higher than that of unmodified biochar. At the initial SO concentration of 50 mg/L, the adsorption efficiency of chitosan-modified biochar (90.94%) was higher than that of biochar (83.41%). The adsorption efficiencies were better at neutral pH of 6÷7. The SO adsorption equilibrium was reached after 240 min of contact time. The results of the study indicated that, chitosan-modified biochar can have extensive application prospects in the treatment of highly colored wastewater containing variety of dyes, including Safranin-O.