A method for the simultaneous separation and determination of vanillin and o-vanillin by capillary zone electrophoresis (CZE) was developed. The influences of type, concentration and pH of running buffer, and applied voltage on separation were investigated. Under the conditions of 50 mmol/L borax-150 mmol/L disodium hydrogen phosphate (pH 7.5) and applied voltage of 15 kV, the vanillin and o-vanillin were separated in 6 min. The method was proved to be robust through verification of accuracy, precision and linearity. The calibration curves of vanillin and o-vanillin showed good linearity in the range of 10-240 mg/L, and the correlation coefficients were 0.999 9 and 0.999 7, respectively. The limits of detection for vanillin and o-vanillin were 1.0 mg/L (S/N = 3). The average recoveries at three spiked levels were 99.4%-101.2% with acceptable relative standard deviations of 0.19%-0.73%. The method has been successfully used for the determination of vanillin and o-vanillin in real samples, and the assay results are satisfactory.