OBJECTIVE：To st udy the chemical constituents of diterpenoids from Buyi medicine Isodon coetsa ，and to provide reference for the development and utilization of the medicinal resources. METHODS ：The 95％ methanol extract of Buyi medicine I. coetsa were isolated and purified with silica gel column ，Sehadex LH- 20 gel column and MCI column. The structures of the compounds were obtained by spectral analysis （mass spectrum ，hydrogen spectrum and carbon spectrum ），and then compared with active components of Miao medicine “Isodon flavidus ”. RESULTS & CONCLUSIONS ：Ten diterpenoids were obtained from I. coetsa，including rabdocoetsin B （Ⅰ），megathgrin B （Ⅱ），rabdocoetsin A （Ⅲ），enanderianin N （Ⅳ），rabdocoetsin D （Ⅴ）， megathyrin A （Ⅵ），lophanic acid （Ⅶ），rubesanolide D （Ⅷ），excisanin D （Ⅸ），excisanin K （Ⅹ）. The compounds Ⅶ，Ⅸ and Ⅹ were isolated from this specie for the first time. Compound Ⅶ（lophanic acid ）is a common active component in the Buyi medicine I. coetsa and Miao medicine “I. flavidus ”.