The invention discloses a device and method for detecting the thickness of the insulation layer of an overhead insulated conductor wire. By using the method for layer thickness detection, a cut detection sample is not needed, thus the problem is solved that the insulation layer is difficult to peel off from the inner core of the conductor wire or part of an insulating material remains inside the conductor wire and accordingly the accuracy of a measurement result is affected. In addition, when the method is used for layer thickness detection, the insulation thickness at a plurality of positionson the overhead insulated conductor to be tested can be measured, thus the problem of big measurement error caused by uneven coating is solved. The device and method for detecting the thickness of the insulation layer of the overhead insulated conductor wire have the advantages of simple structure, low cost, convenient use, easy operation, high accuracy and convenient popularization and use.