Abstract: In order to explore biocontrol strains with nano-selenized ability and develop green antiviral materials to prevent tobacco virus diseases, Pseudomonas fluorescens KBD-1 was identified from the rhizosphere soil of healthy plants in the field with serious tobacco virus diseases. The nano-selenized activity of P. fluorescens KBD-1 was investigated in this study, and its inhibitions against four main tobacco viruses were determined by using the methods including Real-time PCR and Western blot under the treatments of original strain and nano-selenized strain. The results showed that there were high density electron particles outside the nano-selenized KBD-1 and the characteristic absorption peak of selenium appeared at 11.22 keV X-ray. When the concentration of P. fluorescens KBD-1 bacterial fluid after nano-selenization was 5×10⁵ cfu/mL (0.25 mg/L selenium), the control effects against Tobacco mosaic virus (TMV), Potato virus Y (PVY), Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) were all above 88.0%, and the highest control effect against CMV was 91.4%. The treatment at this concentration also had significant growth-promoting effect on tobacco plants. This study showed that P. fluorescens KBD-1 successfully reduced sodium selenite to produce nano-selenium, and enhanced the antiviral activity and growth-promoting effect of the original strain.