UV/Fenton　process　was　employed　to　remove　clopyralid;　meanwhile,　various　UV-based　oxidation　processes　were　compared,　such　as　UV　irradiation,　UV/H2O2,　and　UV/Fe(II).　Results　illustrated　that　UV/Fenton　exhibited　the　highest　degradation　rate,　and　UV　irradiation　alone　hardly　affected　degradation　of　clopyralid.　Rate　constants,　T-1/2　(half-time)　and　E-EO　(electrical　energy　per　order)　were　calculated　to　evaluate　degradation　rate　and　energy　consumption　among　all　these　approaches.　Some　influencing　factors,　such　as　pH,　irradiation　time,　and　molar　concentration　ratio　of　hydrogen　peroxide　to　ferrous　ions,　were　studied　to　obtain　an　optimal　degradation　condition　for　UV/Fenton　process.　To　evaluate　the　efficiency　of　UV/Fenton　process　applied　for　clopyralid　degradation　in　aqueous　solution,　change　of　chemical　oxygen　demand　in　solution　after　UV/Fenton　treatment　was　measured.　Ion　chromatograph　was　used　to　analyze　formation　of　inorganic　ions　and　short-chain　carboxylic　acids　during　photodegradation　process.　It　was　found　that　concentrations　of　chloride　and　ammonium　were　increased　with　irradiation　time,　and　some　short-chain　carboxylic　acids　were　detected.