A　method　based　on　a　linear　model　for　determination　of　the　ionization　constants　(pK(a))　of　some　alkaloids　(benzedrine/BZD,　phenylpropanolamine/PPA,　ephedrine/EPD　and　methylephediine/MEPD)　by　capillary　zone　electrophoresis　with　electrochemistry　detection　has　been　developed.　The　K-a　values　were　obtained　from　the　plots　of　the　reciprocal　of　effective　mobility　against　the　reciprocal　of　concentration　of　sodium　hydroxide.　The　pK(a)　values　evaluated　by　this　method　were　consistent　with　the　values　by　UV,　and　also　agreeable　to　the　literature　values.　The　proposed　method　was　simple,　quick　and　reliable　for　determination　of　the　ionization　constants　(pK(a))　of　alkaloids　simultaneously.