Phosphorus is a non-metallic element essential for all forms of life, and the issue of phosphorus resource scarcity is increasingly gaining attention. Understanding the content and forms of phosphorus in sludge, as well as the technologies for phosphorus recovery from sludge, is of great importance. Firstly, this paper provided a comprehensive overview of various pre-treatment methods (biological, oxidation, acid-base, microwave, ultrasonic, and hydrolysis) for sludge phosphorus recovery, highlighting the potential for combining these techniques to enhance recovery efficiency. Secondly, it introduced the concept of mixed recovery technology for phosphorus in sludge, which involved the strategic arrangement and combination of different treatment technologies. This approach represented a novel and innovative way of addressing the phosphorus recovery challenge. Furthermore, by discussing the effects of various factors on the phosphorus content in sludge, the paper offered an integrated perspective on the complex interplay of these factors, facilitating a more nuanced understanding of the phosphorus recovery process. This review provides a good reference for recovery processes of sludge phosphorus, enabling engineers to select the most appropriate techniques based on specific project requirements.