Guided moderesonanceinadielectricgratingresultsfromaredistributionofenergyinpropagatingwaveswhenhigh orderspatialharmonicsarecoupledtotheleakywave guidemodessustainedbythegrating.Inthispaper,wehaveanalyzedtheguided wavemodesinawaveguidewitharigorouscoupled waveapproach .Fromtheanalyzedresults,wehaveestimatedproperlythelocationoftheguided moderesonanceinaweaklymodulateddielectricgrating .Wealsodiscussedtherelationsamongtheguided moderesonance,gratinglayerthickness,substratethickness,andtheincidentangle.Byadoptingadesignforanti refection ,thesymmetricguided moderesonancewithlowsidebandwasachieved .