简介：ManysocialeventsspreadfastthroughtheIntemetandarousewidecommunitydiscussions.Thoseon-linepublicopinionsemergeintodiversetopicsalongthetime.Moreover,thestrengthofthetopicsisfluctuating.Howtocatchbothprimarytopicsandtrendoftopicsovertheshiftingon-linediscussionsarenotonlyoftheoreticalimportanceforscientificresearch,butalsoofpracticalimportanceforsocietalmanagementespeciallyincurrentChina.Totrythecutting-edgetextanalytictechnologiestodealwithunstructuredon-linepublicopinionsandprovidesupportforsocialproblem-solvinginthebigdataeraisworthanendeavour.Thispaperappliesdynamictopicmodel(DTM)toexplorethechangingtopicsofnewpostscollectedfromTianyaZatanBoardofTianyaClub,themostinfluentialChineseBBSinmainlandChina.Byanalysisofthehotandcoldtermstrends,wecatchthetopicsshiftofmainon-lineconcernswithillustrationsoftopicsofschoolbusandenvironmentinDecemberof2011.Analgorithmisproposedtocomputethestrengthfluctuationofeachtopic.Withvisualizedanalysisoftherespectivemaintopicsinseveralmonthsof2012,somepatternsofthetopicsfluctuationontheboardaresummarized.