The impact strength of polypropylene resin is an important property index. Before using a cantilever beam to measure the impact strength of polypropylene resin, the test spline needs to be injection molded and V-shaped incision made. The article uses two different melting indexes of random copolymer polypropylene resin. By adjusting the injection molding conditions and the notch strength of the spline opening by incision machine, The effects of injection molding conditions and opening depth, incision radian and curvature radius of incision root on the Izod impact strength of two kinds of random copolymer polypropylene were investigated in order to provide a basis for correctly evaluating the impact strength of plastic materials. The results show that the Izod impact strength of random copolymer polypropylene can be improved by reducing the melting temperature of polypropylene, reducing the injection speed and injection pressure, and reducing the holding time. Different opening machines are used to open the injection molded spline, which has a great influence on the impact strength of the spline, and the impact strength of the two polypropylene resins has the same change trend. The shallower the notch depth, the larger the radius of the root curvature, the larger the notch angle, the more concentrated the stress and strain at the notch, and the greater the Izod impact strength of the random copolymer polypropylene.