Abstract: The antagonisms of 63 endophytic bacteria strains isolated from wheat on Sclerotinia sclerotiorum were detected in vitro and in greenhouse.The results showed that 62 strains exhibited antifungal activities against S.sclerotiorum.Among them,6.3％ strains of endophytic bacteria could highly inhibit S.sclerotiorum with inhibition zone more than 10 mm.Seven strains could completely inhibit the formation of sclerotia,and one strain could completely inhibit the germination of sclerotia.In addition,strain Em7 showed strong inhibition to the mycelial growth,sclerotia formation and germination of S.sclerotiorum in vitro.And the biocontrol efficacies of cell-free cultural supernatant of Em7 was 97.5% on Sclerotinia stem rot of canola seedling in greenhouse.According to the morphological,physiological,biochemical characteristics and 16S rDNA sequence,strain Em7 was identified as Bacillus subtilis.The biocontrol efficacy was different when spay the cell free culturel filtrate of Em7 before and after inoculation of S.sclerotiorum.Spaying cell free supernatant 24 h before inoculation of S.sclerotiorum presented the highest control efficacy.Different dilution factor of cell free supernatant showed different inhibitory effects on S.sclerotiorum both in vitro and in vivo.With increasing dilution factor,the inhibition rates to mycelail growth and sclerotia germination decreased,and the biocontrol efficacies declined.Strain Em7 induced alterations on hyphae morphology of S.sclerotiorum,such as leakage,cytoplasm exosmosis and deformation.