Abstract: A method for simultaneous determination of calcium, magnesium and other alkali metal ions in groundwater samples has been perfected by using ion chromatography with IonPac CS12A separation column and 16.8 mmol/L of HCl as eluent. The detection limits (3σ) of the method were 1.5 μg/L and 0.89 μg/L with linear ranges of 0~500 mg/L and 0~250 mg/L for calcium and magnesium, respectively. The reliability of the method was tested by determination of calcium, magnesium and other alkali metal ions in standard samples. The results were satisfactory with precision of 0.19%~1.89% RSD (n=8). No remarkable matrix effect and interference were observed in analysis of the practical samples with the different dilutions. The method is sensitive, rapid, accurate and suitable for the determination of calcium, magnesium and other alkali metal ions in groundwater samples.