The present invention discloses a measuring method for a semiconductor gas sensor based on alternating-current impedance. The method includes the steps: connecting the semiconductor gas sensor to a capacitor in parallel, connecting an alternating-current impedance measuring device to the semiconductor gas sensor and the capacitor, combining measuring parameters under measuring frequencies within a first preset range and parallel capacitance values within a second preset range, and measuring a gas with a known concentration according to each of nine features under each combination; traversing all parameter combinations and all the nine features to obtain a plurality of feature values corresponding to the same gas concentration under each feature; and selecting measuring frequencies within a third range, parallel capacitance values within a fourth range and a certain or several of the corresponding features as measuring parameters finally selected for measuring an unknown gas concentration.