CdTe　colloidal　quantum　dots　(CQDs)　coated　with　glutathione　(GSH)　were　prepared　by　aqueous　synthesis.　Based　on　the　fluorescence　selective　quenching　of　CdTe　CQDs　in　the　presence　of　Cu2+,　the　CdTe　CQDs　were　applied　for　ultrasensitive　Cu2+　sensing.　The　detection　limit　of　Cu2+　concentration　was　0.055　mu　M.　In　order　to　realize　real-time　and　rapid　on-site　detection,　a　capillary　sensor　composed　of　CdTe　CQDs　was　prepared,　and　after　drying　at　room　temperature,　heating　at　high　temperature,　and　laser　processing,　the　sensor　achieved　good　response　time　and　detection　accuracy　results.　The　detection　of　1　x　10(-5)　mol/L　Cu2+　concentration　can　be　realized　in　5-6　s.　Moreover,　the　detection　only　needs　to　be　carried　out　under　an　ultraviolet　lamp,　the　cost　of　the　sensor　is　low,　and　the　detection　method　is　very　simple.　The　sensor　requires　only　3　mu　L　of　solution　to　be　tested　and　can　complete　the　detection,　which　not　only　saves　the　solution　to　be　tested　but　also　greatly　improves　the　limit　of　the　detection　environment.　A　capillary　sensor　is　of　great　significance　for　the　real-time　detection　of　natural　environment　and　industrial　wastewater.