Abstract: An approach to the palaeosalinity, palaeotemperature and palaeoclimatology is treated in this study on the basis of trace elements, major elements and clay mineral compositions in the mudstones from the Cretaceous strata in the Ya'an-Mingshan zone, western Sichuan. The palaeotemperatures in waters were relatively higher, and the palaeosalinities in waters were also noticeably higher from the Early Cretaceous (Jiaguanian) to the Late Cretaceous(Guankouan). The palaeoclimatic conditions displayed the variations of alternating arid and semiarid palaeoclimates in the overall tropical to subtropical zones during the Cretaceous.