IrO2-SnO2　coatings　with　different　Sn　contents　were　prepared　on　titanium　substrate　by　a　thermal　decomposition　method.　The　relationship　between　the　capacitance　properties　and　microstructure　was　investigated　by　means　of　cyclic　voltammetry,　constant　current　discharge　measurements　and　transmission　electron　microscope　(TEM).　Results　show　that　the　specific　capacitance　of　IrO2-SnO2　coating　electrodes　increases　first　and　then　decreases　with　the　Sn　content　increasing.　The　reversibilities　and　fast　charging　and　discharging　behaviors　of　the　electrode　materials　are　improved　gradually.　The　maximal　specific　capacitance　reaches　485.07　F/g　when　the　content　of　Sn　is　70　mol%,　7.5　times　larger　than　that　of　pure　IrO2　electrode.　The　coating　is　of　amorphous　structure,　including　the　nanocrystalline　with　about　1　nm　size　and　narrow　size　distribution,　which　increases　the　active　site　area.