This paper is a review and evaluation of different on-line methods for diagnosing winding fault in induction motors presented in literature. Many methods can be found in literature; in some references, frequency analysis of motor signals such as current, speed, instantaneous power, Parkpsilas vector modulus and so on are introduced. Evaluation of negative sequence of current is also among the proposed methods. Supply voltage unbalance and some other phenomena may be confused with the winding fault. Therefore, the monitoring and fault detection of electrical machines have moved in recent years from traditional techniques to artificial intelligence based techniques. There are many other techniques that will be introduced and investigated in the detailed paper. A comparison of different methods introduced in literature is the main objective of this paper.