Carbon　nanodots　(CNDs)　have　been　widely　applied　in　variety　of　fields,　while　some　evidences　indicate　their　components　may　be　complicated.　In　this　work,　capillary　electrophoresis　(CE)　was　used　to　evaluate　the　effect　of　synthetic　conditions　of　fluorescent　CNDs　prepared　through　the　hydrothermal　method　using　citric　acid　(CA)　and　Triaminoguanidinium　chloride　(TGCl)　as　the　starting　materials.　The　results　indicated　that　the　fluorescent　components　of　the　products　were　affected　by　the　ratio　of　the　starting　materials,　the　reaction　temperature　and　reaction　time.　Under　selected　conditions,　a　ratio　of　TGCl　to　CA　of　1:6,　the　reaction　at　180 °C　for　3 h,　the　product　contains　more　than　4　fluorescent　components　with　similar　optical　properties.　CNDs　were　used　for　the　determination　of　Cr(VI)　in　environmental　samples　with　recoveries　ranging　in　95.3-107%,　and　the　mechanism　was　also　confirmed.