Carbon aerogel is a new kind of materials with extremely low density and abundant porous structure. The researchers have conducted numerous studies on the design, preparation and environmental applications of carbon aerogels and their composites. This review gives an overview on the recent advances of environmental applications of carbon aerogels and their composites, including adsorption of pollutants, separation of oils from water as well as catalytic degradation of pollutants. We also summarize the relationships between the composition, structure and property of carbon aerogels and their composites and elucidate the mechanism of adsorption, absorption and catalytic degradation, as a useful reference for subsequent studies. The future research directions include：screening low-cost organic solid wastes, establishing low-cost, largescale and controlled preparation method, improving performance and recyclability via tuning composition and structure, conducting comprehensive economic-technical analysis and environmental assessment and then promoting the remediation of actual atmosphere, water and soil pollutions.