In the current study, thyme oil nanoemulsion was prepared for controlling of Sclerotinia sclerotiorum. Gas chromatography of thyme oil was performed and exhibited these bioactive components thymol, 1,8-cineole, α-terpinene and ρ-cymene as primary components. The nanoemulsion particles of thyme essential oil was evaluated using DLS. The results indicated that the PS after 30 min of sonication was about 36.65 nm, and Transmission electron microscopy analysis showed a spherical shape. Laboratory investigations showed that nanoemulsions at different concentrations (1000-5000 ppm) inhibited the growth of Sclerotinia sclerotiorum fungus. At a concentration of 3000 ppm, the nanoemulsion completely inhibited fungal growth. Treating fennel seeds with TEON, TEOE and TEOS had little effect on germination inhibition, with nanoemulsion being the most effective in promoting germination, while nanoemulsion was the best in terms of improving seed germination. As a result of nanoemulsion treatment, damping-off rates were significantly reduced, and plant growth was improved.