Abstract: The formation and evolution of ill basin are preliminarily studied in this paper. It is suggested that the ill Basin is a dual formation structure basin formed and developed after is pre-Sinian crystaillne basement experiencing uplift for a rather long period, that is, Carboniferous inland rift basin and past-Carboniferous intermontane terrestrial basin.

Key words: ill Basin, pre-Sinian crystaillne basement: inland rift basin, intermantane terrestrial basin