The invention discloses an interturn insulation detector for a dry air reactor, which comprises a voltage regulator, a transformer, a high-frequency oscillating module and an oscillograph, wherein voltage of an external power supply is regulated by the voltage regulator and delivered to the transformer; the transformer is connected with the voltage regulator; the delivered voltage is regulated to a range required by the high-frequency oscillating module; the high-frequency oscillating module connected with the transformer is connected with the reactor to be detected; evanescent high-frequency oscillation voltage generated by the high-frequency oscillating module acts on the reactor to be detected; and a wave form of oscillating voltage output by the reactor to be detected is detected by the oscillograph.When the detector is in use, lower voltage is applied across the reactor to be detected first, and a wave form of the low voltage is stored by the oscillograph; then higher voltage is applied across the reactor to be detected for one minute, and an output wave form of the reactor is obtained again; the insulating property of the reactor to be detected can be judged by comparing the obtained wave forms at the two times finally, and the purpose of sensitive detection of interturn insulation deficiencies of the reactor is realized.