Abstract: Polystyrene/polypyrrole (PS/PPY) composite microspheres were prepared by seeded emulsion polymerization. When they were utilized as support and reacted with the Mo active center, PS/PPY composite microsphere supported Mo catalysts were obtained. The effect of the characterization of support on the catalytic activity of the polymer supported Mo catalysts was systematically studied. The results indicate that the supported catalyst with hydrophilie nature shows a higher catalytic activity when hydrogen peroxide was used as an oxygen source; the doped ions in the polymer also show effect on the catalytic activity of the supported catalyst, the supported catalyst prepared using ferric nitrate as an oxidant shows the highest catalytic activity, and the conversion in epoxidation of ciscyelooctene can be 90%.