Poly 4-vinylpyridine (P4VP) microspheres between 170 and 728 nm were synthesized by Emulsifier-Free Emulsion Polymerization. The monomer concentration, ionic strength, and initiator concentration affected the microsphere size and size distribution. The increasing monomer concentration led to the increase of microsphere size, whereas the size distribution of the resultant P4VP microspheres increased with the increasing ionic strength of the reaction systems. Mo(O-2)(2)O center dot 2DMF was successfully anchored onto the P4VP microspheres by ligand exchange, and the heterogeneous catalyst showed high-catalytic activity for epoxidation of cis-cyclooctene with environmentally friendly hydrogen peroxide. The size and morphology of the supported microspheres has important influence on the catalytic activity. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3178-3183, 2010