The invention relates to a high-activity heavy petroleum fraction hydroprocessing catalyst and a preparing method thereof. A method of using silica-alumina composite oxide modified by titanium as a carrier to prepare the catalyst is put forward, meso-porous silicon composite oxide prepared through a coprecipitation method is regarded as a substrate material, a synchronous method or a fractional step method is adopted to introduce titanium oxide, or titanium sulfate, or titanium tetrachloride, or N-propyl titanium, or isopropyl titanate or Tetraisobutyl Orthotitanate and the like into the silica-alumina composite oxide, so that a titanium-modified carrier which has a large specific area and a large pore volume is obtained, wherein the specific area of the carrier is 200-310 m<2>/g, and the pore volume is 0.5-1.2 ml/g. A solution impregnation technology is adopted in support of metal active components on the carrier, and the heavy petroleum fraction hydroprocessing catalyst has good hydro-desulfurization and hydro-denitrification activities in heavy petroleum fraction.