A　coupling　method　of　field-amplified　sample　injection　(FASI)　CE　with　amperometric　detection　is　developed　for　ultratrace　analysis　of　ephedrine　alkaloids　stereoisomers.　FASI　was　introduced　by　injecting　electrokinetically　the　sample　solution　for　10　s　into　the　capillary　filled　with　highly　conductive　background　electrolyte　(BGE).　The　diastereomeric　selectivity　and　the　detection　sensitivity　were　improved　by　using　borate　buffer　of　high　ionic　strength　as　BGE.　Parameters　affecting　FASI　and　CE　separation　were　investigated　to　achieve　the　optimal　conditions.　Four　analytes　were　separated　within　15　min　using　200　mmol/L　borate　buffer　(pH　9.5)　and　separation　voltage　of　+18　kV,　with　detection　potential　at　+1.0　V　(vs.　Ag/AgCl)　and　carbon　disc　electrode　as　working　electrode.　Excellent　linearity　was　observed　between　peak　current　and　concentration　of　analytes　in　the　range　of　0.1-100　ng/mL.　The　LODs　(S/N　=　3)　for　(-)-ephedrine,　(+)-pseudoephedrine,　(-)-N-methylephedrine　and　(+)-N-methylpseudoephedrine　were　39.3,　54.9,　30.8,　and　44.1　pg/mL,　respectively.　The　proposed　method　was　successfully　applied　to　the　determination　of　alkaloids　in　Ephedra　sinica,　with　results　agreed　well　with　HPLC　method.　Mean　recoveries　of　102.1-109.7%　and　RSDs　less　than　6%　were　found.　And　the　merits　of　high　sensitivity　and　selectivity,　as　well　as　a　simple　and　stable　operation,　have　been　demonstrated.