OBJECTIVE： To establish a method for the concentration determination of gabapentin （GBP） in human plasma. METHODS： After precipitated by methanol， using sulfamethoxazole as internal standard， LC-MS/MS method was adopted. The determination was performed on Diamonsil C18 column with mobile phase consisted of water （containing 0.05％ formic acid）-methanol using a gradient elution program at the flow rate of 1 mL/min. The column temperature was 30 ℃， and sample size was 20 μL. The ESI was equipped and quantitative analysis was operated in positive ion and MRM mode. The mass transition ion-pairs were followed as m/z 172.0→154.1（GBP） and m/z 279.0→124.0 （internal standard）. RESULTS： The linear range of GBP was 13.4-10 720.4 ng/mL （r＝0.992 3，n＝5）. The limit of quantitation was 13.4 ng/mL， and the minimum detection limit was 4.0 ng/mL. RSDs of inter-day and intra-day were all lower than 10％. Relative errors ranged －4.93％-5.10％. The recoveries ranged 86.2％-90.3％（RSD＜5％，n＝6）， and matrix effects ranged 87.6％-92.1％. The plasma concentration of GBP in 10 epileptic patients ranged 2 075.19-4 078.87 ng/mL （n＝20）. CONCLUSIONS： The method is proved to be sensitive， specific， practical and suitable for plasma concentration monitoring and pharmacokinetic study of GBP in epileptic patients.