A series of carboxylated long chain polyethylene glycols (abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid. These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes. The factors affecting their catalytic properties, e.g. relative molecular mass of polyethylene glycol, reaction temperature, platinum content, and type of alkenes, have been studied. It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain, and increased with reaction temperature. Moreover, these catalysts could be reused several times without a noticeable decrease in activity or selectivity. The reaction pathway leading to excellent selectivity for the beta-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.