The　effect　of　high　voltage　pulse　(HVP)　treatment　on　the　surface　chemistry　and　flotation　behaviour　of　chalcopyrite　and　pyrite　were　investigated　using　single　mineral.　The　results　indicated　that　the　effect　of　HVP　treatment　on　pyrite　was　more　significant　than　chalcopyrite,　both　in　terms　of　size　reduction　degree　and　flotation　behaviour.　Despite　the　stronger　resistance　to　mechanical　breakage　than　chalcopyrite,　the　proportion　of　-0.053　mm　product　of　pyrite　was　higher　than　chalcopyrite　for　12.2　per　cent　in　average　after　HVP　treatment　of　different　pulse　numbers.　The　flotation　recovery　of　chalcopyrite　was　only　slightly　reduced　after　HVP　treatment　of　130　pulse　discharges.　However,　under　the　same　test　conditions,　the　flotation　recovery　of　pyrite　was　reduced　by　64.1　per　cent　in　average.　The　flotation　behaviour　of　the　two　single　minerals　were　in　agreement　with　their　surface　oxidation　behaviour　in　HVP　treatment.　XPS　analysis　and　EDTA　extraction　suggested　that　chalcopyrite　surface　had　only　partially　oxidized　by　HVP　treatment;　whereas　pyrite　was　deeply　oxidized　with　a　large　amount　of　S　element　converted　to　be　sulphate　radicals.　The　relative　permittivity　of　pyrite,　chalcopyrite　and　water　was　33.5,　78.1　and　80　respectively,　which　led　to　a　ratio　of　electrical　field　strength　inside　pyrite,　chalcopyrite　and　water　theoretically　being　2.39:1.02:1.　As　a　result,　pyrite　particles　had　stronger　capability　to　attract　electrical　breakdown　channel　than　chalcopyrite,　and　subjected　to　more　severe　size　reduction　and　surface　oxidation　under　the　same　conditions.　On　the　other　hand,　the　slight　surface　oxidation　of　chalcopyrite　particles　was　hypothesized　to　be　caused　by　the　active　species　((OH)-O-center　dot,　H2O2,　etc.)　formed　during　pulse　discharge.