Several kinds of dichlorobis(beta-diketonato)titanium complexes, i.e., Ti(acetylacetonato )(2)Cl-2, Ti(1-benzoylacetonato)(2)Cl-2, Ti(2,2,6,6-tetramethyl-3,5-heptanedionato)(2)Cl-2 and Ti(4,4,4-trifluoro-1-phenyl-1,3-butanedionato)(2)Cl-2, were synthesized and the corresponding MgCl2-supported catalysts were prepared. by impregnation method. The test of them for propene polymerization revealed that those MgCl2-supported catalysts could be activated not only by methylaluminoxane (MAO) but also by ordinary alkylaluminums as well. The effect of typical Lewis bases on the catalyst performance was investigated in some detail, which indicated that organic silanes are most effective for the improvement of isospecificity of those catalysts.