Abstract: A detection method for interturn short circuit fault in dry-type air-core reactor is proposed using broadband impedance spectroscopy. Firstly, an equivalent distributed circuit model of intact reactor under high frequency is constructed based on the theory of multi-conductor transmission lines, and an equivalent simulation model is established based on the parameter calculation equation of the distributed equivalent circuit to analyze the high-frequency characteristics of the reactor broadband impedance spectrum. Secondly, the amplitude spectrum and phase spectrum of the broadband impedance of the reactor with interturn short circuit fault are simulated to analyze the influence of inductance parameters on the resonant frequency of the reactor impedance spectrum. Finally, an experimental testing was conducted on a small dry-type air-core reactor in the laboratory, which has verified the effectiveness of the proposed method.