Abstract: The investigation of incidence and prime control?measures of tobacco root rot were made in places?such?as Jiaxian and Baofeng in Pingdingshan tobacco plant areas, in order to solve the problem that the quality and products of tobacco were seriously damaged by tobacco root rot caused by fusarium. The?economic?losses caused by tobacco root rot was also calculated. The control efficacy of EM?microbial agent by different manner such as soil application, watering application and foliar?application was studied took the main mariety Zhongyan 100 as?experimental?material. The soil application study showed that treatment at tilling stage, transplanting stage and earthing-up stage together works best. The morbidity?and?mortality were 23% and 16% respectively. The watering application study showed that treatment at tilling stage, transplanting stage, resettling?stage, fast growing stage and topping stage together works best. The morbidity?and?mortality were 18% and 11% respectively. The foliar?application study showed that there was no significant variation between different treatments and the control. Comprehensive results showed that watering application had a remarkable control effect to tobacco root rot. This results provided some theoretical references for the?biological?control of tobacco root rot.