Microplastic pollution (plastic particles<5 mm) is a growing global environmental concern. Its accumulation in soil ecosystems, especially agricultural soils, poses a significant threat to soil health and ecological functions. Biodegradable microplastics (e.g., polylactic acid and polybutylene succinate) are considered eco - friendly alternatives to reduce "white pollution." However, during degradation, they may release more micro - particles, additives, and intermediate products, exacerbating soil pollution. They can also impact soil carbon cycling through various pathways by altering soil structure, microbial activity, and enzyme function. This paper reviews the degradation characteristics of biodegradable microplastics and their effects on soil carbon cycling. It highlights that in agricultural soils, the degradation of biodegradable microplastics is influenced by material properties, environmental conditions, and microbial activity. The degradation products can notably increase soil dissolved organic carbon, boost CO? emissions, and weaken crop photosynthesis and carbon sequestration efficiency. Compared to conventional microplastics, biodegradable ones may intensify short-term carbon cycle fluctuations. Their long-term effects are uncertain due to potential incomplete degradation and additive release. Given this, there"s an urgent need for in-depth research on their far-reaching impacts on soil carbon cycling. Such research can offer a scientific basis for farmland management and sustainable agricultural development.