Abstract: There exists boundary claystone near the boundary between both the marine and terrestrial Permian and Triassic in the eastern Yunnan-western Guizhou area. This paper introduces the characteristics of the boundary terrestrial claystone in the area and discusses its origin. The principal minerals of the claystone are illite-montmorillonite mixed-layer minerals (20% -80%) and kaolinite (35% -80%), and the fragments include zircon, apatite, hexagonal dipyramidal high-temperature quartz and other types of quartz The And microspherules. It is suggested that the terrestrial boundary claystone in the area mainly formed by volcanism, accompanied by normal deposition and influence of impact.