A reliable and sensitive ion chromatography method with solid phase extraction for the determination of oxalic acid in crustacean aquatic products was established. The negative impurities in the extraction solution was precipitated with acetonitrile. The large molecules and Cl- in the supernatant were extracted and purified by the OnGuard Ⅱ RP cartridges and the OnGuard Ⅱ Ag/H cartridges, respectively. The complex matrices sample filtrate was resolved by an IonPac AS11-HC column using hydroxide gradient, which was operated in the online suppression external water mode with suppressed conductivity detection. The results showed that the linear correlation of oxalic acid was good in the range of 0.05~10.00 mg/L (the correlation coefficient was 0.9998). The detection limits (LODs) and the quantitation limits (LOQs) of the method ranged in 0.033~0.041 mg/kg and 0.11~0.14 mg/kg, respectively. The mean recoveries of oxalic acid in crustacean aquatic products ranged from 75.71% to 88.85% with the within-day precisions (n=6) in the range of 1.74%~3.61% and inter-day precisions (n=5) less than 5%. The method was suitable for the quantification of oxalic acid in crustacean aquatic products due to its simplicity and accuracy.