Abstract: From 2004 to 2006, tobacco bacterial wilt disease survey and pathogen isolation were carried out in Yunnan province. In Wenshan prefecture the marjor tobacco plant county, such as wenshan, Yanshan, Guangnan, Xichou and Malipo county, 86.3% disease plant with lower stem black necrotic affect bacterial wilt, 27.7% affect black shank, among 14% plant mixed effect bacterial wilt and black shank. 219 strains of Ralstonia solanacearum are isolated from 258 samples gathered from 12 counties of Yunnan provinces. The pathogen backward inoculation test and ELISA test show that tobacco lower stem black necrotic in Wenshan and Baoshan prefecture is mostly associated with tobacco bacterial wilt, partial with black shank.