Dan-Shen, the roots of Salvia miltiorrhvsa Bnnge (Labiatae),is a well-known Chines traditional drug used for treatment of various kinds of diseases including coronary disorders. In recent years, indeed the alcoholic extract of this drug was found to be effective to some kinds of coronary diseases after clinical trials. So the above extract was subjected to separation work, and therefrom several known components such as tanshinone Ⅰ, tanshinone Ⅱ-A, tanshinone Ⅱ-B, cryptotanshinone, β-sitosterol,(-)-dihydrotanshinone, methyltanshinonate were isolated. Besides, a new compound was also obtained and named methylenetanshinqninone. Its structure was elucidated as a diterpene qninone (Ⅱ) by chemical methods and spectral analyses.