Abstract: It was reported that in the determination of halogen by ion-chromatography in combination with the automatic combustion furnace,the used of C2O2-4 as internal standard was proved to have the distinguishing features of ① clear separation of the halogen (F-,Cl-,Br- and I-),② no significant change of values of peak area of the halogen ions within 3 months and ③ elimination of interferences due to sample matrix and the environmental causes,when Na2CO3/NaHCO3 buffer solution was used as the medium for both the standard solutions and the sample solutions.