Biochar is believed to be promising for soil contaminant stabilization due to its large adsorption capacity. However, study in sediment is rare, especially with the aging effect. In the present study, a plant biomass-derived biochar was added to phenanthrene polluted sediment, in order to investigate its performance in sediment remediation. During the incubation period of 60days, it was observed that the partition coefficient of phenanthrene increased in sediment either with or without biochar addition, as a result of aging process. Whilst, the biochar-added sediments showed much higher partition coefficients, as well as more curved adsorption isotherms, suggesting larger retention of the contaminant. Under the extreme extraction by strong surfactant, the release ratio of phenanthrene from polluted sediment was significantly reduced from 60% to 5% by 0.5% (w/w) addition of biochar. These results suggested that biochar would be applicable for improving the adsorption of organic pollutant in sediment, and the adsorbed organic pollutant would be stably fixed during aging as a result of the increased affinity.