In　the　process　of　embedded　system　modeling　and　performance　evaluation,　the　performance　indicators,　such　as　average　delay,　CPU　occupancy　rate　etc.　,　are　often　need　to　be　evaluated.　In　this　paper,　the　library　functions　of　performance　evaluation　based　on　System　C　language　have　been　designed,　and　the　problem　that　it　could　not　evaluate　the　performance　at　system-level　based-on　system　C　has　been　solved.　The　library　functions　are　designed　for　evaluating　performance　parameters,　calculating　expectations　and　confidence　interval,　and　terminating　the　simulation　when　the　performance　indicators　meet　the　accuracy　requirements.　The　library　functions　can　be　used　in　performance　evaluation　of　embedded　speech　recognition　system　by　evaluating　the　simulation　results,　as　well　as　in　performance　evaluation　of　the　complex　embedded　system　based　on　System　C.　It　is　of　great　value　for　extending　the　library　of　System　C.