B₃(Bacillus sp.) showed powerful inhibition to a wheat pathogen RC-54 (R.cerealis) on 3 media (PDA,NA and K'B),with an effectiveness of 73.7%~99.5% when tested with different methods. Cell-free culture filtrate (CFCF) of B₃ could also inhibit mycelial growth of RC-54. with an efficiency of 80% at the dosage of 12.5%. On PDA medium containing B₃-CFCF, RC-54 needed more days to form sclerotia, and produced a few scle-rotia. When B₃-CFCF was increased to 10%,no sclerotia was formed. And further more, germination of sclerotia was also inhibited by B₃-CFCF. Addition of B₃-CFCF to NB or steriled H₂O with RC-54 mycelia could increase the conductance and infiltration of reducing sugars, amino acids and proteins. Heated B₃-CFCF showed reduced inhibition. Microscopy revealed abnormal, more-branching growth of RC-54 treated with B₃-CFCF.