Inthispaper,twoirreversibleexothermicautocatalyticreactionswhichcarryoutincontinuousstirredtankreactor(CSTR)areconsidered.Adifferential-algebraicsystemisappliedtomodelthesechemicalreactions.Thestabilityandthedynamicbehaviorarestudiedforthedifferential-algebraicsystem.TheHopfbifurcationappearswhentheparameterexceedsacriticalvalue.Inordertoeliminatethiscomplexbehavior,thedifferential-algebraicsystemisdescribedbyasingle-inputandsingle-outputsystemwithparametervaryingwithindefiniteintervals,andthenvariablestructurecontrolwithslidingmodebasedonaspecialpowerreachinglawisdesignedtostabilizethischemicalsystem.Numericalsimulationsaregiventoillustratetheeffectivenessofthemethod.