Theil　index　is　an　indicator　proposed　in　the　field　of　economics,　developed　from　the　concept　of　information　entropy,　used　to　measure　the　degree　of　difference　in　a　system,　and　it　can　consider　both　overall　and　local　differences.　This　article　explores　the　application　of　the　Theil　index　in　bearing　fault　diagnosis　and　proposes　the　correlation　Theil　index　(CTI).　In　order　to　use　this　indicator　in　bearing　fault　diagnosis,　a　tower-shaped　distribution　diagram　called　CTIgram　is　established.　CTIgram　adopts　an　adaptive　multilevel　spectrum　segmentation　method,　which　can　well　obtain　the　center　frequency　and　bandwidth　of　the　fault　signal　and　adaptively　divide　the　frequency　band.　The　frequency　band　selected　by　CTI　often　contains　more　periodic　pulse　information.　This　method　has　great　advantages　in　extracting　fault　information　from　signals　with　noise.　The　proposed　method　is　shown　to　be　effective　by　the　simulation　signal,　and　it　was　proved　by　the　bearing　outer　and　inner　ring　fault　signals　that　this　method　can　be　applied　to　bearing　fault　diagnosis.　The　comparison　experiments　with　fast　Kurtogram　(FK)　and　Gini　index　(GI)　demonstrated　the　superiority　of　the　method.　©　1963-2012　IEEE.