Abstract: The stratigraphic and geographic distribution of early tonsteins in later Permian of south-western China has been systematically studied in this report.By means of contrast and research the eight seams' tonsteins characteristics of the petrography,mineralogy and geochemistry,it can be confirmed that all the tonsteins are the alkalinityvolcanic ash derived tonsteins from different age.This finding has filled the recording gap of alkalinity-volcanie ash sediment in the coal formation of the world.Besides,it has a important application value and theoretical significance.