Abstract: Crystal Ⅸ, C₁₇H₁₆O₃, is a new compound isolated from the Chinese drug Dan-shen (Salvia miltiorrhiza Bunge). On the basis of its UV, IR, NMR, MS spectrum data as well as its chemical reactions, it is deduced to structure B, named Dan-shen spiroketallactone, which is comfiremed by X-ray diffraction analysis. The space group of IX is PZ₁Z₁Z₁. There are four molecules in a unit cell with parameters a=25.931, b=7.622, c=6.770, v=1338.06.