Biochar (BC) is widely used for activation of persulfate (PS) to remove difficult-to-degrade organic pollutants in water due to its good activation performance, low cost and environmental protection. Different modification methods can enrich the active sites on the surface of BC, further enhance the physicochemical properties of BC, and improve the activation performance and stability. This paper firstly reviewed the modification methods of biochar applied to activate PS, secondly summarized the reactive sites of BC activation of PS, the free radical and non-radical pathways of PS activation and their differences, and analyzed the modification and the effect of biomass feedstock on the transformation between the two different activation pathways, and finally looked forward to the development direction of BC activated PS application and mechanism research.