The paleographic pattern of the southern margin of the South China Block before the Cenozoic is essential for understanding the formation and evolution of the South China Sea. Hainan Island, located at the northern margin of the South China Sea and adjacent to the southern edge of the South China Block, serves as a key region for investigating the paleographic features of the passive continental margin of the South China Sea. In this study, we conducted biotite 40Ar/39Ar geochronological analysis on granites from the Triassic to Cretaceous on Hainan Island, to explore the exhumation characteristics and topographic evolution during the Mesozoic. The results show that the cooling ages obtained from biotite 40Ar/39Ar range from 107 to 92 Ma The consistent cooling ages of granitic plutons along the periphery of Hainan Island suggest that the Hainan Island underwent rapid cooling during this period. By synthesizing the available biotite 40Ar/39Ar age data, we observe a “younger on the periphery, older in the center” cooling age distribution, indicating that during this period, the peripheral regions of Hainan Island experienced more significant exhumation than the central areas during this time. It is inferred that during the Late Mesozoic, Hainan Island exhibited a “high in the periphery, low in the center” topographic pattern. Based on this observation, we evaluate and select samples suitable for paleoelevation reconstruction, using detrital zircon Eu/Eu* anomalies and whole-rock (La/Yb)N and Sr/Y ratios. The results of paleoelevation reconstruction of the peripheral regions of Hainan Island during the Cretaceous indicate that the paleoelevation in this period exceeded 3000 meters. Rapid exhumation of the peripheral granitic plutons provided a substantial detrital material to the low-lying Baisha Basin in the central region, further supporting the “higher in the periphery, lower in the center” topographic feature. A comprehensive analysis of the geochronological, geochemical, and provenance data from the South China Sea peripheral blocks reveals that the region experienced a widespread exhumation/cooling event during the Early-Late Cretaceous. This suggests that, at least during the Late Mesozoic, the southern and northern margins of the South China Sea still existed as a unified entity, implying that the initiation of the South China Sea rifting occurred after this period.