Abstract: Polylactic acid (PLA) is an environmentally friendly, biodegradable polyester; however, it is also a flammable material. To broaden its application scope and ensure safe usage, it is essential to conduct research on flame retardant modifications for this material. This paper examines the flame retardant effects of modified synergistic agents and microencapsulated ammonium polyphosphate (APP) on PLA composite materials, while also introducing various types of modified synergistic agents. A comparative analysis is conducted to evaluate the performance characteristics of different flame retardant systems. Finally, this study outlines future directions for the modification of PLA flame retardants, emphasizing that the development of environmentally friendly, low-additive flame retardants will be a significant trend in forthcoming research endeavors.