The invention is a preparation method of a biaxially stretched film special material for homopolypropylene, which comprises mixing raw material propylene with a mixture of a main catalyst, a cocatalyst and an electron donor, first pre-polymerizing, and then sending the pre-polymer into a series connection. The two loop reactors are polymerized, and the polymer is flashed, deactivated, dried, pelletized and packaged. The main feature is that the main catalyst uses 1.80-3.80% titanium and 15.0-20.0% magnesium. The efficient catalysts, as well as the granulation process, use different antioxidants, slip agents and stabilizers than the prior art. Due to the adoption of high-efficiency catalyst and homemade additives, the invention has excellent product quality, the melt index is 2.4-3.2g/10min, the isotacticity is 94-96%, and the ash content is less than 200ppm. The polypropylene of the present invention is used for biaxially stretching film speeds of up to 400 m/min, with low film breakage and uniform film thickness distribution.