Biochar has gained significant attention in the field of sewage treatment, both domestically and internationally, due to its favorable adsorption capabilities and low cost. While ordinary biochar does exhibit certain adsorption effects, its performance is less effective when dealing with high concentrations or specific pollutants. However, the performance of modified biochar in sewage treatment shows significant improvement compared to unmodified biochar. Modification processes result in a larger specific surface area, larger pores, and a higher concentration of functional groups. These modifications not only enhance its adsorption capability, but also enable the specific adsorption of organic pollutants, making it highly valuable in the treatment of aquaculture wastewater. This paper provides a review of the recent research status of biochar at both domestic and international levels, highlighting several common methods of biochar preparation and modification, as well as discussing their respective advantages and disadvantages. The mechanisms of action of biochar and its application in the treatment of aquaculture wastewater are explained, while also exploring the factors that have hindered the development and adoption of biochar. Countermeasures and suggestions are proposed, along with a prospect of its application prospects in the field.