Abstract: The treatment of a large amount of residual sludge from sewage treatment plants has consistently been a research priority and hotspot. Furthermore, the conversion technique of sludge into sludge-based biochar by pyrolysis can not only deal with the residual sludge, but also facilitate its reuse in the sewage treatment. The sludge-based biochar has garnered growing attention for its application in wastewater treatment, especially in the emerging pollutants removal. The sludge-based biochar from the sewage sludge was functional in the field on heavy metals, organic matter, and emerging pollutants by preparation methods, pyrolysis temperature, and modification methods. Moreover, it visually illustrated the mechanisms and functions of these transformations through charts and diagrams. This paper provides more ideas for future research and the practical application of sludge biochar in addressing the removal of heavy metals, organic matter, and emerging pollutants.