With　consideration　that　the　controller　parameters　may　vary　from　the　designed　value　when　the　controller　is　realized,　based　on　Lyapunov　stability　theory,　a　design　method　of　nonfragile　guaranteed　cost　control　for　a　class　of　Delta　operator-formulated　uncertain　time-delay　systems　is　studied.　A　sufficient　condition　for　the　existence　of　the　nonfragile　guaranteed　cost　controller　is　given.　A　numeric　example　is　then　given　to　illustrate　the　effectiveness　and　the　feasibility　of　the　designed　method.　The　results　show　that　even　if　the　parameters　of　the　designed　controller　are　of　variations,　the　closed-loop　system　is　still　asymptotically　stable　and　the　super　value　of　the　cost　function　can　also　be　obtained,　while　the　closed-loop　system　will　be　unstable　if　the　variations　of　the　controller　parameters　are　not　considered　when　the　controller　is　designed.　The　nonfragile　guaranteed　cost　controller　derived　from　the　traditional　shift　operator　method　may　cause　the　closed-loop　system　to　be　unstable,　while　the　nonfragile　guaranteed　cost　controller　based　on　Delta　operator　method　can　avoid　the　unstable　problem　of　the　closed-loop　system.　©　2010　South　China　University　of　Technology,　Academy　of　Mathematics　and　Systems　Science,　Chinese　Academy　of　Sciences　and　Springer-Verlag　Berlin　Heidelberg.