A new fault diagnosis technique for rolling element bearing using multi-scale Lempel-Ziv complexity (LZC) and Mahalanobis distance (MD) criterion is proposed in this study.A multi-scale coarse-graining process is used to extract fault features for various bearing fault conditions to overcome the limitation of the single stage coarse-graining process in the LZC algorithm.This is followed by the application of MD criterion to calculate the accuracy rate of LZC at different scales,and the best scale corresponding to the maximum accuracy rate is identified for fault patt recognition.A comparison analysis with Euclidean distance (ED) criterion is also presented to verify the superiority of the proposed method.The result confirms that the fault diagnosis technique using a multi-scale LZC and MD criterion is more effective in distinguishing various fault conditions of rolling element bearings.