The K-Ar isotopic ages of 23 Paleogene basalt specimens collected from Jianghan Basin were determined and isochrones were made according to different horizons.Isochron dating results are given as follows:the 4th member of Qianjiang Formation(E
q
4
)is 41.0 Ma;Jingsha Formation(Ej)
45.5 Ma;Xingouzui Formation (Eχ)
51.2 Ma;Shashi Formation (Es)
62.4 Ma.The results are generally coincident with their stratigraphic times. Based on the results
the Paleogene geochronologic scale of the basin that is closely related to volanic activites has been made.