Abstract: In order to determine Cd isotopic composition accurately, the key is to guarantee Cd recovery and reduce Sn interference.The recoveries of Cd with various separation and purification methods reported by previous studies show a large range variation from 42.6% to 99.8%, and the removal efficiency of Sn interference are various(87.8%-97.4%).Both the Cd recovery and Sn removal are not ideal.Reported in this study, 0.1 mol/L HBr-0.5 mol/L HNO₃ mixture was determined to be a more effective solution to separate Cd from Sn.By increasing the amount of this mixture during leaching, more Sn can be removed from the samples without Cd loss.When 30 mL of mixture is used during leaching, more than 99.8% Sn can be leached out from the sample and the Cd recovery is 99.0%±0.5%.This method can be utilized for Cd isotope analyses of soil samples, offering new insight for high-precision Cd isotope measurement and serving as a technical method for Cd pollution tracing in the study of environmental soil.