A method of ion chromatography and direct conductivity detection was established to determine three pyridinium ionic liquid cations,eg 1 ethyl pyridinium cation(EPy+),1 butyl pyridinium cation(BPy+) and 1 hexyl pyridinium cation(HPy+).The effects of eluent types,eluent concentration and column temperature on retention of the cations were investigated with sulfonic acid base cation exchange column using ethylenediamine-citrate acid-acetonitrile as eluent.The result indicated that,with the increase of column temperature,the retention times of pyridinium cations were reduced,so the retention process of pyridinium cations is exothermic.The retentions of pyridinium cations accord with carbon number rule.The optimum chromatographic conditions were as follows:mobile phase:02 mmol/L ethylenediamine-03 mmol/L citrate acid-3% acetonitrile(pH 44);flow rate:10 mL/min;column temperature:45 ℃.Under the optimum conditions,three pyridinium cations were successfully separated.The detection limits(S/N=3) for EPy+,BPy+and HPy+were 060,159,108 mg/L,respectively.Relative standard deviations(n=5) for peak areas were less than 12%.The method was applied in the determination of pyridinium ionic liquids synthesized in chemical laboratory with spiked recoveries of 100%-104%.The good linearity and repeatability of the method made it meet the requirements of quantitative analysis.