In order to improve the bioleaching effect of low-grade chalcopyrite ore from Yongping Copper Mine using mixed thiobacillus ferrooxidans and thiobacillus thiooxidans,the catalytic effect of silver ion added in the solution on the bioleaching of the chalcopyrite ore was investigated by tests in shaking flasks.The results show that the addition of silver ion can greatly accelerate the dissolution velocity and the leaching rate of copper at the initial stage of the bioleaching,in which the dosage of 10 mg /L of silver ion is most beneficial to the dissolution of copper and after 600 h bioleaching the leaching rate of copper can be increased from 20% to 65% with 45% increase comparing with that without addition of silver ion.The addition of silver ion obviously depressed the dissolution of iron and the bacterial oxidation of Fe2 in solution.At the presence of sliver ion,the low oxidation potential was more favorable to the copper dissolution than the high potential for low-grade chalcopyrite ore.