The utility model provides a transformer copper clad aluminium winding detector, the detector include that one connects transformer winding and produces sine wave signal's low -frequency signal generator to transformer winding, low -frequency signal generator and transformer winding's lead end connect a signal processing unit through same frequency sampling unit respectively, and transformer winding's lead end still is connected with the voltage current sample unit that can gather sampling signal, signal processing unit the signal integration carries out and calculate after export the AC resistance slope under each frequency the image display unit of connection to, signal processing unit calculates under each frequency the AC resistance slope of fine copper according to the frequency of gathering and exports to and connect the image display unit simultaneously, detection method go on according to alternating current skin effect's principle, it is high more to exchange the frequency promptly, the skin depth of electric current is shallow more, the AC resistance that records is just big more, thereby whether the effectual wire that detects out is the copper -clad aluminum wire circle.