The invention discloses a method for manufacturing a semiconductor thin-film material. The method comprises the following steps of: in the manufacturing process of a surface acoustic wave gas sensor, dispensing a mixed solution containing triethanolamine and a carbon nano tube on a delay line of a double delay line-type oscillator, and drying in vacuum to form a sensitive film. According to the invention, the polymerized sensitive film is prepared by adding the ground carbon nano tube to the triethanolamine; and compared with the pure triethanolamine sensor, the triethanolamine/carbon nano tube sensor has greatly improved sensitivity, stability and detection quality.