So far the volcanic material has rarely been found in karst bauxite, and the direct evidence of volcanic material participating in mineralization of karst bauxite needs to be further clarified.Methods:Based on line survey and section study，such as microscopic observation and elemental analysis of rocks and oresResults: A mass of of volcanic ash is observed in bauxite and early aluminite rocks within western Guangxi, with at least 30% content; and the types of volcanic ash include detritus, crystal fragment, hyaloclastic fragment, volcanic dust, with significantly Plastic or semi- plastic deformation and obviously rigid burst, and showing freely- falling. and deposited in situ or half in situ; and the volcanic ash is easy to decompose into boehmite, kaolinite, hematite and other fine minerals, and the clastic volcanic ash is easier to mineralize than the dusty one, and a lot of volcanic ash had made directly bauxite mineralization. Element geochemical characteristics of bauxite and bauxitic rock show that the volcanic ash had originated in magma, and the discrimination diagram of immobile elements of bauxite and bauxitic rock and dating data indicate that the ash had been mainly made of alkaline basalt magma from Ailaoshan—Songma volcanic arc, which is consistent with the modern island arc volcanic rocks,.the Emeishan igneous rock had taken park in mineralization too duing the diachronism of bauxite formation. Owing abundance and long duration, the volcanic ash may be the cause of the mass extinction at the end of Guadalupian. Conclusions: Bauxite mineralization had been developed directly by volcanic ash, and the volcanic ash had mainly come from the Ailaoshan—Songma orogenic belt, partly from Emeishan igneous rock; and the volcanic ash may be the cause of the mass extinction at the end of Guadalupian.