Soil acidification affects the ecological environment of farmland and severely restricts the improvement of crop quality and yield. The use of soil amendments is an effective measure to alleviate soil acidification and is also a hot topic in soil science research. Biochar, due to its unique structural characteristics and physicochemical properties, shows tremendous potential in reducing soil acidity, alleviating plant aluminum (Al) toxicity, improving soil structure, increasing soil fertility, and enhancing microbial activity. This paper explores the potential mechanisms of biochar in alleviating Al toxicity, systematically summarizes its regulatory effects on soil pH and Al forms in acidic soils. It discusses the mechanisms and influencing factors of biochar in altering the structure and fertility of acidic soils, elucidates its impact on the microbial community structure and function in acidic soils, analyzes potential issues in the process of biochar improving acidified soils. The aim is to provide references for the efficient and sustainable utilization of biochar and contribute insights for the development of acidified soil amendments.