Some novel half titanocene catalysts containing phosphodiesterase isooctyl (p204) were synthesized and their catalytic performances for the copolymerization of ethylene-propylene were investigated. The results showed that the half titanocene catalysts had a good catalytic activity in the copolymerization of ethylene-propylene. The catalytic properties of the catalysts were effected by the ligand p204, the mass of propylene in gas reactants, the reaction temperature and the pressure of copolymerization reaction, and the ratio of methylaluminoxane (MAO)/Ti.