OBJECTIVE： To adopt ion suppression chromatography to determine related substance in ibandronate sodium raw materials.  METHODS： The separation was performed on a Dionex IonPac AS11-HC column with mobile phase consisted of potassium hydroxide （gradient elution） at the flow rate of 1.1 mL/min. The column temperature was set at 45 ℃， and sample size was 20 μL. Suppressed conductivity detector was adopted with temperature of 35 ℃. RESULTS： The linear ranges of phosphite， impurityⅠand phosphate were 3.08-30.83 μg/mL（r＝0.999 9）， 2.84-28.43 μg/mL（r＝0.999 1）， 2.95-29.52 μg/mL（r＝0.999 9）， respectively. The limits of quantitation were 2.47， 56.7， 3.31 ng， and the limits of detection were 0.75， 17.2， 1.0 ng. RSDs of precision， stability and reproducibility tests were all lower than 4.0％. The recoveries were 101.49％-103.57％ （RSD＝0.7％，n＝9）， 100.00％-104.85％（RSD＝1.8％，n＝9）， 101.35％-104.08％ （RSD＝0.9％，n＝9）， respectively. CONCLUSIONS： The method is simple， accurate and sensitive， and is suitable for the determination of related substance in ibandronate sodium raw materials.