OBJECTIVE： To establish a method for simultaneous determination of sodium valproate （VPA） and its metabolite 2-propyl-2-pentenoic acid （2-ene-VPA） in human plasma.  METHODS： Plasma sample was extracted with cyclohexane and experienced derivatization with 2，4′ -dibromoacetophenone using n-octanoic acid as an internal standard. RP-HPLC method was adopted. The determination was performed on Zorbax SB-C18 column with mobile phase consisted of acetonitrile-water （65 ∶ 35，V/V） at the flow rate of 1 mL/min. The column temperature was set at 35 ℃， and UV  dectection wavelenth was set at 258 nm. The sample size was 20 μL. RESULTS： The linear range of VPA and 2-ene-VPA were 5.0-200.0， 0.5-20.0 μg/mL （r＝0.999 9，n＝5）. The limits of quantification were 5.0， 0.5 μg/mL. RSDs of inter-day and intra-day were all lower than 5％. Method recoveries were 95.99％-98.80％ and 97.40％-98.17％， and extraction recoveries were 80.46％-86.23％ and 80.45％-85.61％. The plasma concentrations of VPA in 10 epileptic children were 27.4-93.2 μg/mL， and those of 2-ene-VPA were 0.85-3.94 μg/mL， respectively. CONCLUSIONS： The method is simple， specific and suitable for plasma concentration determination and pharmacokinetic study of VPA.