Biodegradable plastics are considered ideal replacements for traditional plastics due to their easy biodegradability, and have broad application prospects. Soil is an important destination for various biodegradable plastic waste. A comprehensive understanding of the ecological effects of biodegradable plastics in the soil environment can provide a scientific basis for evaluating the ecological safety of biodegradable plastics, which is the foundation and prerequisite for their large-scale promotion and application. Given that microbial degradation is the main pathway for the degradation of biodegradable plastics in soil, a thorough understanding of the degradation process and mechanism can provide theoretical guidance for achieving efficient and controllable in-situ degradation of biodegradable plastics. This paper first summarized the ecological toxicological effects of biodegradable plastics on soil ecosystems from the perspectives of soil physicochemical properties, soil microorganisms, plants, and animals. Biodegradable plastics entering the soil environment are not only a physical input, but also a chemical input, which can change the physicochemical properties of soil, such as bulk density, porosity, and nutrient content. They can directly or indirectly affect the structure and function of soil microbial communities, and affect the growth and development of plants as well as the survival and reproduction of soil animals. Furthermore, the microbial degradation mechanism of biodegradable plastics in soil and the key factors affecting degradation efficiency were further summarized. Soil microorganisms degrade biodegradable plastics mainly through three key steps: colonization on the plastic surface, secretion of extracellular enzymes that catalyze polymer depolymerization, and mineralization of oligomers or monomers. The degradation rate of biodegradable plastics in the actual soil environment is relatively slow, and their degradation efficiency is affected by various factors such as the properties of plastics, soil environment, and climate conditions. At the same time, the microorganisms and enzymes involved in the degradation of biodegradable plastics were systematically combed. Because of the current research status and shortcomings, the key research directions in the future are prospected, aiming to provide scientific reference for the study of environmental impacts and microbial degradation of biodegradable plastics in soil.