Modified bitumen is a critical material to ensure the durability of asphalt pavements. Traditional polymer-modified bitumen (PMB) has been widely researched and applied in the past two to three decades. Recently, a high-content SBS (Styrene-Butadiene-Styrene) polymer-modified bitumen (HSBSMB) with a higher SBS content of up to 7–9% by weight has started attracting interest from researchers. There are, however, still few specifications or technical guidelines for HSBSMB. To gain a better understanding of HSBSMB, the composition and structure of typical polymer SBS and base bitumen, the micromorphology and micromechanics of HSBSMB, its rheological and aging characteristics, as well as its asphalt mixture and field pavement performance were reviewed comprehensively in this paper. The content covered in this paper is primarily derived from 210 pertinent papers published between 1990 and 2023 in two databases, Web of Science and Google Scholar. It appears from our review that HSBSMB has a stronger internal polymer network than conventional SBSMB and thus exhibits better resistance to rutting, fatigue, and cracking as well as better aging resistance. Furthermore, findings from both laboratory scale and field pavement scale indicate that HSBSMB not only offers higher performance and durability but also leads to reduced pavement structural layer thicknesses in ensuring performance. However, many issues and challenges still remain before HSBSMB will become a viable option for large-scale application in road infrastructure, aspects such as the mechanism of its internal structural changes, the optimization of methods for evaluating its rheological properties, the life cycle assessment of its long-term benefits, as well as the storage stability and workability of HSBSMB. It is hoped that this review will contribute to a better understanding of HSBSMB and promote its application.