According to IEC and national standards，the turn-to-turn insulation of dry-type air-core reactorswith nominal system voltage 35k V and below could be tested by either the lightning impulse or the turn-to-turn over-voltage． But both the lighting impulse test and the turn-to-turn over-voltage test will be carried out according to theregulations of the IEEE and industrial standards． In order to make it clear that how to test is more reasonable，tak-ing a series of reactor and a shunt reactor for example，numerical analyses on the inductance variation of the reactorwith a turn-to-turn failure are carried out in this paper． The effectiveness of the turn-to-turn failure predication forthese two test methods is researched by the circuit simulation，and the experimental verification is accomplished on a wound reactor sample． Ｒesearch results indicate that，when the dry-type air-core reactor has a turn-to-turn fault there is a smaller inductance variation． The misjudgment may occur if the turn-to-turn failure is detected by light-ning impulse waves． Moreover，the turn-to-turn over-voltage test is simpler to detect the failure． It is consideredthat doing two kinds of test is necessary，and it is suggested to accept the test method which is provided by IEEEand industrial standards．