Abstract: In order to direct tobacco bacterial wilt disease control and forecast, the dynamic of tobacco bacterial wilt in Yunnan province were carried out through period field roots survey and ELISA test. In the high disease incidence field in Wenshan prefecture, roots samples detect Ralstonia solanacearum positive firstly at five weeks after transplant (w.a.t), and only several tobacco plant roots show black necrosis. At 7 w.a.t, 50% roots samples detect R.solanacearum positive, roots black necrosis plant incidence increase rapidly, while stem show no obvious symptom. At 9 w.a.t, 50% roots samples detect R.solanacearum positive, roots black necrosis plant incidence up to 50%, while several plant show stem black necrosis; At 12 w.a.t, stems R.solanacearum positive percentage, black necrosis roots incidence and black necrosis stems incidence up to 80%. The period of roots samples with high R.solanacearum positive, roots displaying symptom and stem displaying symptom occurs successively at certain interval (about 21 days). Root samples with R.solanacearum positive time and roots black necrotic emerge time could server as a basis of decision of first chemical applying period. The confirmation result of ELISA test show that R.solanacearum type colony could isolated form the ELISA test positive samples, and the type culture also show R.solanacearum positive when tested by ELISA.