Abstract: The mass spectral interference existed in the process of Cd isotopes analysis by mass spectrometry, including ¹¹⁰Pd, ⁷⁰Zn⁴⁰Ar, ⁹⁵Mo¹⁶O, ¹¹²Sn, ¹¹³In, ¹¹⁴Sn and ⁹⁸Mo¹⁶O. Therefore, in order to avoid mass spectral interference of Cd isotopes, there should be separated before the isotope analysis. A hydrochloric acid system was used as a commonly method to separate Cd, but the elution of Sn was difficult and the volume of elution was large. Aiming at the above problems, a method for separating Cd in hydrobromic acid system using anionic resin AG-MP-1M was developed. After the sample was completely digested by the mixed acid, the sample was dissolved with 1 mL 0.25 mol/L hydrobromic acid. After loading on the column, washing 3 mL 0.25 mol/L hydrobromic, most ions such as Sn, Zn, Mo could be separated, and other elements such as Pb were washed with 1 mL 2 mol/L hydrochloric acid and 3 mL 0.5 mol/L hydrochloric acid, and Cd was rinsed with 3 mL 0.002 mol/L hydrochloric acid. By these processes, the yield of Cd is 99.1%, and the interference elements such as Sn, Zn, and Mo can be completely separated. Comparing with the method reported in the literature, this separation method of Cd significantly reduces the elution volume. The total elution volume is 10 mL, and Sn and Cd can be completely separated. This method improves the separation efficiency of Cd, which can be used in the measurement of Cd isotopes and Cd concentrations.