Abstract: A method of on-line dialysis with ion chromatography was used to quantify levels of available fluorine in topsoil samples. The topsoil samples were extracted by ultrasonic wave. The upper clear solution was on-line treated with dialysis and then separated with the Metrosep A Supp 4-250 Anion Exchanger Column. A mixed solution of 1.8 mmol/L Na₂CO₃ and 1.7 mmol/L Na₂HCO₃ was used as the mobile phase. Comparing with the routine analysis method, this new method is simple and avoids complicated pretreatment of the sample. The recoveries of the method ranged from 90.5% to 95.7% with a precision of 1.60% (RSD, n=6).The results indicate that this method is fast, convenient, sensitive, and suitable to quantify levels of available fluorine in topsoil samples.