Abstract: Based on the thin section observasions and diagenetic study,the fluid inclusions from Kela-2 gas pool,the present largest gas reservoir of the country are analysed,resulted in the parameters of trapping temperature and salinity of abiogenic inlusions in salty fluid associated with organic inclusions,and physical parameters and compositional data of organic inclusions,thus the sequential order of fluid inclusion formation can be inferred,and the palaeogeotemperature gradients of different diagenetic phases in upper Cretaceous calculated by a linear regression. Finally the infilling phases,and characteristics of evolution and migration of oil/gas,and resources potential in Kela gas pool are analysed.