In this paper, the preparation technology, rheological properties, and modification mechanism of rubber powder/SBS composite modified asphalt were systematically studied. The preparation process and parameters of rubber powder/SBS composite modified asphalt were determined as follows: the SBS was developed for 3 hours followed by the addition of rubber powder, with a development temperature of 180±5°C. The content of stabilizer was 2‰, the content of compatible agent (furfural extraction oil) was 3.0%, the content of rubber powder was 18–20%, and the content of SBS was 2.5–3.5%. Three indexes-elastic recovery test, segregation evaluation methods, and viscosity evaluation methods – were used to analyze the effect of modifier content on the macro properties of asphalt. Based on rheological principles, multiple stress repeated creep recovery tests (MSCR) and low temperature bending beam rheological beam tests (BBR) were carried out on rubber powder/SBS composite modified asphalt. On this basis, after fitting and analyzing the low-temperature creep compliance curve using the Burgers viscoelastic model, the asphalt was assigned a low-temperature viscoelastic assessment index. The modification mechanism of the modified asphalt was analyzed using scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). The results showed that the amount of modifier had an obvious influence on the microstructure of the modified asphalt.