Basedoncontinuummechanics,wehavedevelopedamodelforsemi-quantitativeestimatingeffectsofphasecontinuityonflowstrengthoftwo-phaserocksincludingpartiallymeltedorcrystallizedrocks.Calculationsofthebulkflowstrengthofcompositerocksasfunctionsofthevolumefraction,geometricalshapeandcontinuityoftheconstitutivephasesinvolveinnumericallysolvingtwonon-linearequationsandthusareeasytobeperformed.Themodelhasbeenjustifiedbyagoodagreementbetweenthepredictedandmeasuredresultsondiabase(64%clinopyroxeneand36%plagioclase)intherangeofexperimentaltemperaturesandstrain-rates.Itisbelievedthatthepresentmodelcouldprovideanapproximateestimatefortherheologicalevolutionofmagmaticrocksduringtheirlifecycleofmelting-crystallization-deformation.