The present invention relates to a supported catalyst containing titanium, its preparation and it use in the homo-, co-, and ter-polymerization of olefin-unsaturated compounds. The present invention also relates to a catalytic system comprising a supported catalyst based on titanium and a co-catalyst selected from organo-derivatives of aluminum. More specifically, the present invention relates to catalyst supported on silica, obtained by reacting a titanium halocarboxylate and a magnesium halocarboxylate with an aluminum chloroakylderivative, in the presence of a carrier consisting of high porosity silica. The above reaction essentially takes place in the pores of the silica itself.