As an important conductive polymer, poly (3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS) has been gradually applied to the field of gas sensors due to its simple preparation method, high conductivity, stable chemical properties and unique sensing mechanism. However, the preparation of PEDOT:PSS-based gas sensing materials with high sensitivity and good selectivity is still a huge challenge. At present, a lot of research work on this subject is in progress. On the basis of related research work, the research progress of gas sensors based on PEDOT:PSS and its composite materials in recent years was reviewed, and focused on the gas sensing properties and mechanism of pure-phase PEDOT:PSS, PEDOT:PSS and polymer composites, PEDOT:PSS and inorganic semiconductors (metals and metal oxides), and carbon materials. As well as, the development trends of PEDOT:PSS and its composite materials in structure and process were summarized and prospected.