The turn-to-turn overvoltage test for dry-type air-core reactors has been accepted by many standards.The test equipment which meets standards is needed to ensure the implementation of standards.The development on this turn-to-turn overvoltage test equipment for dry-type air-core reactors and the experimental research is carried out in this paper.It is found that the stabilized impulse oscillator voltage cannot be applied on the reactor by the standard recommended circuit because of the decrease of natural spark-discharge of sphere gaps under the repeat discharge condition.This problem is solved by an improved circuit with controllable discharge gaps.Results of turn-to-turn overvoltage tests on a reactor with imitating turn-to-turn faults in different locations certify that the developed equipment can identify the turn-to-turn short circuit fault by contrasting oscillator voltage waveforms.Research results indicate that controllable discharge gaps for the turn-to-turn overvoltage test circuit are necessary.It is suggested to be recommended by standards.