Abstract: To explore the evolution characteristics of the Cretaceous paleoclimate in the Yong'an Basin in western Fujian and the influence of the Late Mesozoic geomorphic changes along the coast of South China on the paleoclimate in the southeastern margin of South China, the Cretaceous stratigraphy of the Bantou, Shaxian, and Chong'an formations in the basin was taken as the research object. The fine-grained clastic rock samples were collected and examined for major and trace elements and rare earth elements distributions, and their sedimentary and paleontological characteristics were compared and analyzed. Variations in the paleoclimate of the Yong'an Basin in western Fujian during the Cretaceous period were clarified. Results show that the early Cretaceous Bantou Formation reflects a changing climate condition. The value ranges of CIA (chemical index of alteration) (69.91～85.29), Rb/Sr (1.13～2.21), Mg/Ca (0.57～3.57), Sr/Cu (5.44～11.66), and the calibrated paleosalinity index 100*Sr/(BaAl₂O₃) (CPI) (1.18～1.55) collectively suggest a scheme transition from a warm-humid climate to a dry-hot environment. Moreover, the redox discrimination indices δCe (0.89～1.03), V/Cr (1.03～1.57), and Ni/Co (2.34～10.58) signaled a dominant weak oxidation environment, aligning with the transition to dry-hot climate in the early Cretaceous. Moving to the late Early Cretaceous to Late Cretaceous, Shaxian Formation and Chong'an Formation samples manifest further shifts in climate dynamics. The value ranges of CIA (67.14～75.68), Rb/Sr (0.99～9.05), Mg/Ca (0.37～16.22), Sr/Cu (1.20～15.46), and CPI (0.50-1.77) expose a change from hot-dry to warm-humid, followed by a transition to cold-dry climate. The δCe value (0.89～1.03), V/Cr (0.51～1.72), and Ni/Co (1.45～6.45) point to alternating weak oxidation and weak reduction environments, aligning with the multiple climate shifts during this period. Therefore, the Cretaceous paleoclimate of the Yong'an Basin exhibits a complex transitional sequence in climate, oscillating from dry-hot to warm-humid and then to dry-cold conditions, often with extreme climates. By comparing the paleoclimate between the study area and the surrounding South China region, it is evident that the predominant transformation in the inland South China paleoclimate was from warm-wet to dry-hot conditions. The paleoclimate transitions between the coastal and inland regions of South China reflect the response to late Mesozoic coastal geomorphic changes in the South China coastal areas.