ThispaperderivestheLindellformulabasedonthegeneralizedvariationalprinciple.ForthecomplexdielectricconstantmeasurementofasmalllossydielectricrodwithRayleigh-Ritzmethod,anaccuratevariationalanalysisisgiven.Theconceptofcomplexfrequencyisintroducedingeneral,andthestabilityofthesolutionisdiscussed.Comparingwiththeresultofperturbationmethod,itisconcludedthatthedeviationofperturbationalgorithmshouldbetakenintoconsideration.