A paired ion chromatographic method was developed for rapid determination of theanine in tea. SDS was added as a paired ion reagent, mobile phase was a mixture of acetonitrile and phosphoric acid aqueous solution, detection wavelength was set at 200 nm. The retention time of Theanine was 6.27 min. The calibration of theanine was in good linearity in the range of 0.04-20μg with the regression equation Y=1.51466×10^6X＋3,28706×10^5（r^2=0,99901）. The detection limits was 1.15 ng（S/N = 3）, This method is rapid, simple, and accurate for the analysis of theanine in tea.