Abstract: This paper discusses the research progress of organic thin film transistors (OTFT) gas sensors in the State Key Laboratory of Electronic Thin Films and Integrated Devices of University of Electronic Science and Technology of China, under the support of the National Natural Science Foundation of China. In this work, organic thin film transistor with a bottom-gate bottom-contact type structure was used as the sensor element, the preparation process and structure parameters of the device were optimized, and the sensing properties of copper phthalocyanine (CuPc) film to H₂S were studied. Besides, the OTFT gas sensor based on P3HT-ZnO nanorods composite film, P3HT single-layer film, P3HT-MoS2 composite and layered film was fabricated. Furthermore, the electrical properties and gas sensing performance of OTFT device were analyzed systematically.