Based on the thin section and cathodoluminescence，a comprehensive study of the filling sequence of diagenetic minerals in T2l4 is carried out by using the geochemical data of diagenetic minerals fluid inclusions and Sr，C，O isotopes，etc.，to clarify the sequences and sources of diagenetic fluid in Leikoupo Formation，Western Sichuan Basin. The results show that the filling minerals of different grain sizes in T2l4 in Western Sichuan Basin can be divided into three stages with filling sequences as follows：micro-powder dolomite and calcite（the first stage）→fine-grained dolomite and calcite（the second stage）→meso-crystalline dolomite，calcite and intercalated dolomite（the third stage）. The three stages by which fluid accumulating are roughly corresponding to the early to late of Late Triassic（232-214 Ma），the end of Late Triassic to the end of Late Jurassic（212-145 Ma），and early Cretaceous to the end of late Cretaceous（142-70 Ma），respectively. The C，O，Sr isotopes of matrix dolomite and pore fillings in T2l4 show that the diagenetic fluid has the geochemical characteristics of normal marine carbonate rocks，and it is revealed that the high value of 87Sr/86Sr diagenetic fluid in T2l4 is from the fluid intrusion of capillary concentration，infiltration and backflow in the syngenetic-quasi syngenetic period under the environment of evaporating tidal flat，and the release of sealed seawater during the burial period.