Abstract: To study the impact of microbial agents on tobacco root growth and soil moisture conditions under drought stress, the amount of root nutrition, growth, fresh and dry weights of tobacco roots were studied with different degrees of drought stress by controlling irrigation on Luyan 1 by using pot experiment. The results showed that a certain amount of microbial agents can promote Luyan the 1st root growth and root uptake of nitrogen, phosphorus, potassium, and increase root fresh and dry weight. In addition, under the same drought conditions, with the increase of microbial agent application, the soil moisture rate was higher, indicating that the microbial agent may improve soil moisture by reducing water using efficiency of tobacco. In this study the best results were obtained when 45 g/pot microbial agent was applied and when the irrigation amount was 120 mm, 160 mm, and 120 mm at the root spreading stage, the vigorous growing stage and the maturing stage respectively.