Abstract: An ion chromatography method for the determination of sulfate content in agar was established. After being degraded the organic components of agar via ashing, the samples were dissolved in ultrapure water, then filtrated by a membrane of 0.45 μm.The sulfate was detected by DIONEX ICS-3000 ion chromatography equipped with a conductivity detector, ASRS 4 mm suppressor and IonPac AS23 column, using 9.0 mmol · L^-1 Na₂CO₃ and 1.6 mmol · L^-1 NaHCO₃ as eluents. The flow rate of eluent was 1.0 mL · min^-1. The results showed that the detection of sulfate had good linearity within concentration range of 1.0 mg · L^-1 to 15.0 mg · L^-1 (R²=0.9995). The detection limit of this method was 0.1 mg · L^-1, and the recoveries of spiked matrix ranged from 89% to 102%. Compared with the traditional methods, ion chromatography was simple, rapid, accurate and sensitive.