Abstract: A new sesquitetpene lactone, tentatively named yejuhua lactone (Ⅰ), proved to be a compound of unsaturated guainolide type, was isolated from Chrysanthemum indicum L. On the basis of the IR., UV., and experimental results, it was shown that the compound possessed the following functional groups: tertiary alcohol, conjugated double bond, 1,2-epoxy, and carbon bridge. We succeeded in obtaining chamazulene, identified by the visible spectrum and also the melting point, 131.5-33℃, of TNB salt of the known compound, by selenium dehydrogenation of yejuhua lactone. Catalytic (Adams) reduction of (Ⅰ) in ethyl acetate gave (Ⅱ), and afforded (Ⅲ) in acetic acid. LiAlH reduction of (Ⅰ) gave (Ⅳ). Chromic acid oxidation of (Ⅲ) gave (Ⅵ). The course of the reaction is as follows: Firstly, compound (Ⅰ) was catalytically reduced in acetic acid and then followed by oxidation, where upon a ketone was isolated from the resulting products. The presence of epoxide group linking on the five member ring probably attached to 1, 2 position was ascertained from IR. data, ν_max^nujal 1737 cm^-1 of (Ⅵ). The infrared absorption spectra of (Ⅰ) and its derivatives were proved to be all concorded to the above structural formulas. The study of orientation of the functional groups is in progress.