Abstract: According to the characteristics of cyanidation silver slime with high selenium， the silver slime was pretreated by controlled electro chlorination， and the silver chloride in the leaching residue was reduced by polyhydroxy aldehyde. The results show that the optimum conditions of controlled electro chlorination process are as follows： the mass ratio of cyanidation silver slime to sulfuric acid is 5：3， the mass ratio of cyanidation silver slime to sodium chloride is 5：1， the liquid-solid ratio is 3：1， and the final potential of chlorination reaction is 750 m V by adding Na Cl O₃； the technological conditions of silver reduction by polyhydroxy aldehyde from leaching residue are as follows： the mass ratio of silver chloride to polyhydroxy aldehyde is 4：1， the mass ratio of silver chloride to alkali is 5：3， and the liquid-solid ratio is 6：1. Under the optimum conditions， the direct yield of silver is 99 %， the grade of silver in crude silver is 99 %， and the index is good.