An on-line removing matrix method with pre-concentration of the analytes was developed for the simultaneous determination of impurity anions（e.g.chloride,sulfate） in ink dye by ion chromatography（IC）.The sample was diluted with de-ionized water,filtrated by 0.22 μm nylon membrane and then injected into the IC system directly without any further pretreatment.The sample solution in the loop was delivered by de-ionized water,and then filtrated on line by DIONEX OnGuard II P column and IonPac NG1 column for pre-removing of dyestuff and hydrophobic components.The analytes flowing out in the dead time were concentrated in the high capacity anion-exchange guard column IonPac AG11-HC.The concentrator then stepped in the IC system when the valve switched to injection mode.The chloride and sulfate were separated on a DIONEX IonPac AS23（4 mm×250 mm） column by using 4.5 mmol/L Na2CO3 -0.8 mmol/L NaHCO3 as the eluent at a flow rate of 1.2 mL/min.The analytes were detected with a Dionex DS6 conductive detector and quantitively analyzed by the external standard method.The results indicated that the linear ranges of Cl－and SO2-4 were 0.05-5.0 mg/L（r=0.999 8） and 0.1-10 mg/L（r=0.999 7）,respectively.The average recoveries were in the range of 94%-103% with relative standard deviations（RSDs） no more than 1.0%.The detection limits（S/N=3） were 0.02 mg/L for Cl- and 0.05 mg/L for SO2-4.The method was applied in the determination of chloride and sulfate in ink dye samples with satisfactory results.