Abstract: Aiming at the problem of difficult to diagnose local defects of aero-engine intershaft bearing,a new diagnosis approach of sideband difference diagnostics of local defects for aero-engine intershaft bearing was proposed in this paper.Based on operating characteristic of intershaft bearing for both inner and outer ring rotation,the approach used signal modulation frequency sideband as the main fault information,and established a complete set of fault diagnosis procedure.Experiments of an aero-engine inter bearing with the outer ring failure were carried out.Using the proposed approach,the local defects of the bearing was judged accurately.The theoretical analysis and fault bearing diagnosis example showed that the method can identify local defects of intershaft bearing and is effective in local defects diagnosis for the aero-engine intershaft bearing