Abstract: Quasi-RP-HPLC was applied to the determination of caffeine (CAF) in tea drinks. The sample was separated on high-purity silica-gel column by elution with a mixture of acetonitrile and 0.03 mol·L-1 sodium formate of pH 2.9 (5+95) as mobile phase. Flow-rate of the mobile phase was set at 1.0 mL·min-1, and diode array detection at 274 nm was adopted in the determination. Linear relationship between values of peak area and mass concentration of caffeine was obtained in the range of 0.2-1 000 mg·L-1, with detection limit (3S/N) of 0.05 mg·L-1. The proposed method was applied to the analysis of tea drinks, giving values of recovery obtained by standard addition method in the range of 95.6%-104%.