Abstract: The samples were collected in the western part of Chinese Southern Tianshan Mountains．The rock types for Ar-Ar analysis are andesite in the Wupataerkan Group of the Silurian to Devonian age and quartz andesite breccia in the Kangkelin Formation of the Carboniferous to Permian age．The plate and isochron ages of the former sample are 427.70±0.60 Ma and 426.96±4.57 Ma respectively；and those of the latter sample are 288.16± 0.40 Ma and 289.．18±2.02 Ma，respectively．The 40Ar-39Ar geochronologic date reported here provide new information for the study in the Chinese Southern Tianshan orogenic belt．