InthedischargeofEASTtokamak,itisobservedthat（2,1）neoclassicaltearingmode（NTM）istriggeredbymodecouplingwitha（1,1）internalmode.Usingsingularvaluedecomposition（SVD）methodforsoftX-rayemissionandforelectroncyclotronemission（ECE）,thecouplingspatialstructuresandcouplingprocessbetweenthesetwomodesareanalyzedindetail.TheresultsofSVDforECErevealthatthephasedifferencebetweenthesetwomodesequalstozero.Thisisconsistentwiththeperfectcouplingcondition.Finally,performingstatisticalanalysisofγ1/1,ζ1/1andω2/1,wefindthatγ1/1moreaccuratelyrepresentsthecouplingstrengththanζ1/1,andγ1/1isalsostronglyrelatedtothe（2,1）NTMtriggering,whereγ1/1isthewidthof（1,1）internalmode,ζ1/1istheperturbedamplitudeof（1,1）internalmode,andω2/1denotesthemagneticislandwidthof（2,1）NTM.
