We described a facile approach to controllably synthesize silver nanoparticles with various morphologies using N, N-dimethylformamide (DMF) in the presence of poly (vinyl pyrrolidone) (PVP). Triangular/hexagonal nanoplates, chain-like nanoplate assemblies, and nanobelts could be selectively obtained. On the basis of the experimental results, the concentration of poly (vinyl pyrrolidone) and AgNO3, reactive temperature and time were the vital factors to determine the shape of final products. Reasonable mechanisms for the formation of silver nanoparticles with various morphologies were proposed. Fluorescence modulation of dye rhodamine B (RhB) and fluorescein (FI) in the presence of silver nanoparticles were studied. Addition of silver nanoparticles could produce fluorescence enhancement and show self-quenching release of RhB, while the fluorescence intensity of FI decreased due to the presence of the silver nanoparticles. The effects of silver nanoparticles on the fluorescence properties of dyes were dependent on the competition between the local field enhancement and non-radiation energy transfer from the molecule to the metallic nanoparticles.