The　binding　constants　between　bovine　serum　albumin(BSA)　and　each　of　two　diuretics　(hydrochlorothiazide　and　bumetanide)　were　determined　by　capillary　electrophoresis-amperometric　detection　(CE-AD)　on　the　basis　of　mobility　shift　method.　The　optimal　conditions　were:　an　uncoated　fused-silica　capillary(70　cm　X　25　μm　i.　d.　),　neutral　H　3　BO　3　-Na　2　B　4　O　7　-NaCU(Palitzsch,　pH　7.4)　buffer　solution,　800　mV　for　working　potential　,　9　kV　for　separation　voltage　and　9　kV　x　8　s　for　electrokinetically　injection.　Under　the　optimum　conditions,　the　binding　constants(K　b　)　of　these　two　compounds　were　2.45　x　10　4　L/mol,　1.　19　x　10　4　L/mol　for　hydrochlorothiazide　and　bumetanide,　respectively.　The　experiment　al　results　indicated　that　the　Kb　values　evaluated　by　this　method　were　nearly　consistent　with　those　by　UV　spectrophotometry.　The　results　showed　that　the　CE-AD　method　is　simple,　fast,　and　accurate　for　the　measurement　of　the　binding　constants　of　diuretics-protein.