OBJECTIVE： To establish a method for simultaneous determination of impurity E， impurity Ⅰ and impurity Ⅳ in crude drug and preparation of esomeprazole sodium. METHODS： LC-MS/MS method was adopted. The separation was performed on Agela VenusiL MP C18 column with mobile phase consisted of acetonitrile-water （gradient elution） at the flow rate of 0.2 mL/min. The column temperature was 35 ℃， and the sample size was 1 μL； analytes were analyzed by electro-spray ionization （ESI） in the multiple reaction monitoring mode， negative ion. The precursors of production transitions m/z 360.1→194.0 （impurity E）， m/z 375.8→210.7 （impurity Ⅰ）， m/z 330.2→312.1 （impurity Ⅳ） were used to measure impurity. RESULTS： The linear range of impurity E， impurity Ⅰ and impurity Ⅳ were 0.001 26-0.044 80 μg/mL （r＝0.994 7）， 0.001 34-0.045 2 μg/mL （r＝0.992 8） and 0.018 9-1.260 00 μg/mL （r＝0.991 4）. The limit of quantitation were 0.001 26， 0.001 34， 0.018 9 μg/mL； the detection limits were 0.000 41， 0.000 44， 0.006 3 μg/mL. RSDs of precision and reproducibility tests were all lower than 4％； RSDs of stability tests of impurity E and impurity Ⅰ were all lower than 10％（n＝5）， and that of impurity Ⅳ was higher than 15％ （n＝7）. The average recoveries were 87.69％-100.72％ （RSD＝4.29％， n＝9）， 90.04％-100.63％（RSD＝3.67％，n＝9）and 93.58％-101.86％（RSD＝2.66％，n＝9）.  CONCLUSIONS： The method is accurate， rapid， sensitive， selective and suitable for the content determination of 3 impurities in crude drug and preparation of esomeprazole sodium.