This study developed a novel waste rubber powder modified high-modulus asphalt based on composite modification technology. The preparation process was determined by orthogonal tests, and the mechanical properties of modified high-modulus asphalt were evaluated through rheological tests in comparison with three common high-modulus asphalts to verify its application potential. The modification mechanism of modified high-modulus asphalt was characterized by Fourier transform infrared spectroscopy and fluorescence microscopy tests. The results show that the recommended mixing ratio of modified high-modulus asphalt is 20% waste rubber, 6% ethylene-vinyl acetate copolymer, and 4% ammonium polyphosphate. Although the high temperature performance, rutting resistance, and fatigue performance of modified high-modulus asphalt are slightly inferior to those of high-modulus asphalts prepared with two polymer modifiers, they are significantly better than those of hard asphalt, and all mechanical properties meet the application requirements of high-modulus asphalt. Compared with other asphalts, modified high-modulus asphalt exhibits the most prominent low temperature performance. The microscopic test results indicate that the modification process of modified high-modulus asphalt is chemical modification with minimal swelling, and no obvious network structure is formed inside.