The invention discloses a preparation method for a tungsten-oxide-nanosheet-structured gas sensor working at room temperature. The preparation method comprises the steps that a ceramic wafer substrate is cleaned, a platinic interdigital electrode is prepared on the ceramic wafer substrate, a solvothermal reaction solution is prepared, a tungsten-oxide-nanorod-structured gas sensor is prepared through a solvothermal method, an aluminum oxide substrate after a solvothermal reaction is cleaned, and thermal treatment is performed on elements of the tungsten-oxide-nanorod-structured gas sensor. According to the preparation method, the tungsten-oxide-nanosheet-structured gas sensor can be prepared at low cost. According to the solvothermal method, operation is easier, the technological conditions needing to be controlled are few, and no pollution to the environment is generated. The preparation method for the tungsten-oxide-nanosheet-structured gas sensor which can detect nitrogen oxide gas with the extremely low concentration (can reach 0.1 ppm) and is high in sensitivity and rapid to respond/recover is supplied, and the important practice and research significances are achieved.