The invention discloses a gas sensor fiber membrane and a preparation method. The gas sensor fiber membrane is formed by composite fiber materials through hot pressing, and the composite fiber consists of organic high molecules with the weight average molecular weight between 50 and 500 thousand and inorganic molecules, wherein the organic high molecules are selected from polyvinyl acetate, polyethylene oxide, polyvinyl alcohol, polylactic acid, polylactic acid-glycollic acid copolymers and polycaprolactone, the inorganic molecules are selected from tin acetate, palladium chloride, sodium chloride, calcium acetate and zinc butter, the organic high molecules and the inorganic molecules are mixed into electrostatic spinning solution after being respectively prepared into solution, then, the electrostatic spinning solution respectively carries out processes such as electrostatic spinning, hot pressing, high-temperature calcination and the like, and the gas sensor fiber membrane is prepared. The gas sensor fiber membrane has the characteristics of ultrahigh sensitivity and high selectivity, in addition, the microporous structure can be maintained at a high temperature, the preparation method is simple, the operation is easy, and the preparation method has wide application prospects in many fields.