Abstract:Garcinia xishuanbannanensis Y. H. Li is a rare tree species belonging to the Guttiferae and endemic in Xishuangbanna District of Yunnan. From its stem-bark two polyisoprenyl benzophenones-xanthochymol and isoxanthochymol have been isolated. They were identified on the basis of physico-chemical properties and UV, IR, 1HNMR, 13CNMR and MS analysis. The test of antitumor and antibacteria properties of these two compounds in mam- mals will be reported subsequently.