The　electrode　materials　have　a　decisive　effect　on　the　performance　of　supercapacitors.　IrO2-Co3O4/Ti　composite　material　was　prepared　by　a　thermal　decomposition　method.　The　first-principles　calculation　was　used　to　study　the　effect　of　Co　content　on　the　electronic　structure　of　IrO2-Co3O4.　The　influence　of　the　Co3O4　content　on　the　microstructure　and　electrochemical　performance　of　the　electrode　was　analyzed　in　detail.　First-principles　calculation　revealed　that　the　coating　with　the　50%　mol　Co3O4　was　in　a　full　conductive　structure,　and　the　density　of　states　of　the　composite　oxide　with　excessive　content　of　Co3O4　would　shift　to　a　higher　energy　level　and　generate　a　band　gap.　Co　doping　could　inhibit　the　crystallization　of　IrO2.　The　50%IrO2-50%Co3O4/Ti　electrode　exhibited　the　most　obvious　coexistence　of　crystalline　and　amorphous　phases.　Besides,　the　addition　of　Co3O4　changed　the　microstructure　to　a　ring-shaped　branched　structure,　which　effectively　increased　the　specific　surface　area　and　total　pore　volumes　of　the　coating.　The　electrode　with　the　50%　Co3O4　had　the　maximum　capacitance　value　of　979.6　F/g　and　maintained　90%　of　its　initial　capacitance　even　after　20,000　cycles　of　constant　charge-discharge　cycles,　which　was　an　ideal　electrode　material　for　supercapacitors.　The　results　from　first-principles　calculation　and　the　experiments　were　in　consistency.