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　mu　m　i.d.),　neutral　H3BO3-Na2B4O7-NaCl(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　K-b　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.