Abstract: In order to solve the problem of prevention and control of tobacco bacterial wilt in acidic soil, an acid-resistant antagonistic bacteria CLP-6 was obtained by rapid screening of biocontrol bacteria based on rapid screening of biocontrol bacteria. The antagonistic activities of CLP-6 were observed by scanning electron microscope, the types and contents of extracellular bacteriostatic substances were determined with HPLC-MS techniques. Moreover, the inhibitory effect of screened strains on R. solanacearum was detected by fluorescence quantitative PCR. The results showed that the R. solanacearum was destroyed and killed by extracellular antagonistic substances of this strain, and pH 5.5 conditions were suitable for the growth of the strain CLP-6, and the extracellular bacteriostatic protein and 2,4-DAPG were high. Strain CLP-6 could significantly reduce R. solanacearum gene copy numbers in rhizosphere soil and stem base of tobacco at pH 5.5 and pH 7.0, and the inhibitory effect was better under the pH 5.5 soil condition. When inoculated for 192 h, the gene copy numbers of R. solanacearum in tobacco rhizosphere soil treated with CLP-6 decreased by 98.12% and 96.25% respectively compared with CK treatment. When inoculated for 144 hours under pH 5.5 soil condition, the gene copy numbers of R. solanacearum in tobacco stem base was the lowest in the CLP-6 treatment and significantly lower than that in the CK treatment. Strain CLP-6 was identified as Pseudomonas protegens combined with 16S rRNA, rpoD and rpoB gene sequences analysis. The new acid-resistant CLP-6 strain has an important development potential in reducing the infection of R. solanacearum in continuous cropping acidic soil and improving the green control of tobacco bacterial wilt.