Traditional polymer styrene-butadiene-styrene (SBS) modified asphalt is considered to have poor compatibility and is easily isolated during production and transportation. The storage stability and compatibility of modified asphalt can be significantly improved by polyphosphoric acid. Therefore, the research status of polyphosphoric acid/SBS composite modified asphalt was reviewed. The preparation process of polyphosphoric acid/SBS composite modified asphalt was systematically summarized, with a focus placed on the modification mechanism and road performance of polyphosphoric acid/SBS composite modified asphalt. The results indicate that the high-temperature performance, anti-aging performance, and fatigue performance of asphalt can be significantly enhanced by polyphosphoric acid/SBS modified asphalt. The influence on water stability is found to depend on the type of compound matrix asphalt and the gradation design of the mixture. Whether the low-temperature performance is improved remains inconclusive and requires further exploration. Finally, the future research direction of polyphosphoric acid/SBS composite modified asphalt is prospected.