Fluorescent Ag nanoclusters are of significant interest because they provide the bridge between atomic and nanoparticle behavior in noble metals. Herein, microwave irradiation was originally used for the synthesis of water-soluble fluorescent Ag nanoclusters. As-prepared Ag nanoclusters present red fluorescence emission around 608 nm and a characteristic absorption peak at about 508 nm. Transmission electron microscopy (TEM) shows an average size of 1.6 nm for Ag nanoclusters. The effect of solution pH on the synthesis process and optical properties of Ag nanoclusters was investigated. The pH-dependent present form and adsorption capacity of poly(methacrylic acid, sodium salt) (PMAA) ligands are believed to be the reason for the pH effect.