OBJECTIVE： To establish and validate the method for the determination of carbamazepine （CBZ） in human plasma， and to apply the method for external quality assessment. METHODS： After precipitated with acetonitrile， the plasma sample was determined by LC-MS/MS. Using loratadine as internal standard， the determination was performed on Kromasil C18 column with mobile phase consisted of water （containing 0.1％ formic acid）-acetonitrile （gradient elution） at flow rate of 0.6 ml/min and column temperature of 40 ℃. The ion transitions under MRM mode by ESI+ ionization were performed at m/z 237.1→194.0 and m/z 383.1→267.0 for CBZ and internal standard， respectively. RESULTS： The linear range of CBZ were 5-1 000 ng/ml （r＞0.998）. The limit of quantitation was 5 ng/ml. RSDs of inter-day and intra-day were 1.00％-6.42％； relative deviation were －6.93％-0.32％. The external quality assessment of 5 samples were 679.0， 475.0， 104.0， 29.2 and 26.2 ng/ml， respectively. The pass rate of assessment result was 100％. CONCLUSIONS： The method is sensitive， accurate and specific. The method is applicable for the plasma concentration determination and external quality assessment of CBZ.