Abstract: A strain of Fusarium arthrosporioides was isolated from the soil of Qinghai-Xizang plateau and its nitrogenous secondary metabolites were investigated. A white crystallinepowder was extracted from solid medium cultures of Fusarium arthrosporioides. According to spectrometric data (IR, NMR, MS) and the degradation products, it was firmly identified as enniatin B. The results of pharmacological activity tests showed that enniatin B had comparatively strong activity against acetylcholine on isolated rat intestines. Isolation of enniatin B from F. arthrosporioides has not been previously reported.