The invention discloses a stannic oxide hollow porous film gas sensitive element and a preparation method thereof. The gas sensitive element is characterized by covering a thin film formed by a single-layer stannic oxide hollow sphere on a substrate accompanied by an electrode, wherein the thickness of the thin film is 90 to 130nm, the diameter of the hollow sphere is 90 to 130nm, the wall thickness is 15 to 25nm, the diameter of each particle forming a sphere wall is 15 to 25nm, and the pore space between each two particles is 2 to 4nm. The method comprises the steps of adding stannic chloride pentahydrate into an ethanol water, stirring, adding a hydrochloric acid solution to obtain a mixed liquor, carrying out sealed reaction on the mixed liquor, carrying out solid-liquid separation on the mixed liquor, and washing to obtain a stannic oxide hollow sphere; adding a mercapto-type modifier into a stannic oxide hollow sphere ethyl alcohol dispersion liquid, stirring, carrying out solid-liquid separation, and washing to obtain mercapto-modified stannic oxide hollow sphere; adopting an air-water interface self-assembly method for self-assembling the mercapto-modified stannic oxide hollow sphere on a water surface so as to obtain a single-layer stannic oxide hollow sphere thin film, using the substrate accompanied by the electrode for fishing out, and drying to obtain a target product. The stannic oxide hollow porous film gas sensitive element is easy to be widely used in high sensitivity trace detection of methyl mercaptan gas.