Abstract: To explore the effects of pH on the growth characteristics of R. solanacearum in tobacco, the incidence of tobacco bacterial wilt in R. solanacearum-mixed soils at different pH values was analyzed. The population dynamics of R. Solanacearum at different pH values were determined by qRT-PCR, and the variations of biofilm and motility of R. solanacearum were detected by the crystal violet method and semi-solid medium method respectively. The results showed that severe tobacco bacterial wilt occurred in weakly acidic and neutral soils (pH 6.0-7.0). The population of R. Solanacearum was maximum (9.1×10⁸ cfu·g^-1 FW) in the soils at pH 6.5. The biofilm formation ability of R. Solanacearum was the strongest and the weakest at pH 5.5 and 7.0, respectively. The motility of R. solanacearum was the strongest and the weakest at pH 6.5 and 8.0, respectively. Therefore, soil pH influences the infection ability of R. solanacearum by affecting the population dynamics, biofilm formation ability and motility of R. solanacearum.