Abstract: Bismuth impurity in copper electrolyte could be efficiently removed by solvent extraction. The performance of extracting bismuth with N235 was investigated by adding assisting extraction agent into aqueous phase. The effects of various factors such as volume fraction of N235, concentration of assisting reagent, volume ratio of organic to aqueous phase (V(O)/V(A)), reaction time and temperature on bismuth extraction ratio were investigated. The results show that volume fraction of N235, concentration of assisting extraction agents and phase ratio are the main factors influencing the bismuth extraction ratio. The optimal extraction condition is as follows: the sulfuric acid concentration is 3.0 mol/L; assisting extraction agent concentration is 0.1 mol/L; volume fraction of extraction N235 in the organic phase is 20 %; the phase ratio is 1:1; and extraction time is 5 min. Under the optimized condition, the one-stage extraction efficiency of bismuth is 97.3 %.