Silver nanoparticles have been widely used in consumer products due to their excellent antimicrobial properties. Release of nanosilver into natural waters may induce negative environmental impacts on local microorganism communities. This work evaluated the influence of anions such as sulfate, phosphate, chloride and sulfide on the toxicity of silver nanoparticles. Results revealed that sulfide anion could significantly reduce their toxicity in comparison with other anions, which provides an in-depth investigation on the toxicity control of released silver nanoparticles.