Abstract: Fine particulate matter (PM_2.5) is a critical environmental factor that currently affects human health. It primarily enters the body through inhalation and can induce adverse health effects in multiple systems, including respiratory, cardiovascular, nervous, and digestive systems. The homeostasis of gut microbiota is crucial for human health, and gut microbiota may exert multiple effects through the regulation of immune function, metabolic balance, and neural signal transmission. Recently, more and more studies have indicated that exposure to PM_2.5 may alter the composition and richness of gut microbiota and play a crucial role in the development and progression of various diseases through multiple pathways. Given the close interaction between PM_2.5 exposure and gut microbiota, we comprehensively reviewed the effects of ambient PM_2.5 exposure on gut microbiota and the potential underlying mechanisms based on existing epidemiological and toxicological studies. Additionally, the role of gut microbiota in the adverse health effects induced by PM_2.5 exposure, particularly in the context of gut-lung, gut-brain and gut-liver axis were also explored here.