Highly stable Ag NPs were synthesized using anionic polyacrylamide (APAM) as the template and reductant. When APAM concentration was 1.50 mu M, as-prepared Ag NPs with the diameter of about 3.8 nm had a quantum yield as high as 1.51%. When adding Cu2+ and Hg2+ into the Ag NPs solution, the fluorescence was quenched effectively. The response between the fluorescence intensity and metal ions concentration allowed for a linear relation, and the detecting limitation for Cu2+ was lower than 1 x 10(-9) mol/L.