The invention discloses an iron core reactor inter-turn defect test circuit and method to solve a conventional iron core reactor inter-turn defect test method. The method comprises a lightning impulsetest, a pulse oscillation withstand voltage test and the like, wherein the result of the lightning impulse test is related to the turn insulation of the iron core reactor, but only the incoming waveend of a winding be checked and the test voltage is much higher than a power frequency withstand voltage peak so that a technical problem arises that the lightning impulse test is not effective on theinter-turn defect in the middle of the winding of the iron core reactor. The pulse oscillation withstand voltage test can be used for the detection of the turn insulation of an air reactor. However,due to problems such as a small number of turns and the core saturation of the iron core reactor, the turn insulation test cannot use the air reactor test method so that a technical problem arises that it is impossible to guarantee nonoccurrence of core saturation at doubled fundamental nominal voltage.