Wind turbines proliferation in industrial and residential applications is facing the problem of maintenance and fault diagnosis. Periodic maintenances are necessary to ensure an acceptable life span. The aim of this work is to develop theoretical tools to diagnose the failure or the malfunction of the doubly-fed induction generator (DFIG). The diagnosis method is based on the impedance spectroscopy which is used for the diagnosis of batteries, fuel cells, and electrochemical systems. This first attempt for using this method to the diagnosis of the DFIG provides good results for the detection of the grounding connection, short circuit and stator resistance variation.