Abstract: AIM　To study the sterol constituents in the mycelia of Mycena dendrobii Fan et Guo. METHODS　Various column chromatographies with silica gel were employed for the isolation and purification. The structures of compounds were elucidated by spectral analysis. RESULTS　A new ergosterol oxide (1) 6,9-epoxy-ergosta-7,22-dien-3-ol and a known compound β-sitosterol have been isolated, and the structure of compound (1) was established on the basis of its IR, ¹HNMR,　¹³CNMR,HMQC,HMBC and MS spectra. CONCLUSION　Compound 1 is a new compound.