Nurliah, NurliahSukendi, SukendiSiregar, Yusni IkhwanSiregar, Sofyan2018-04-032018-04-032018-04-03978-602-51349-0-6wahyu sari yenihttps://repository.unri.ac.id/xmlui/handle/123456789/9343This research is to know the composition of tree species and diversity of tree species that found in Undisturbance forest at Tahura Sultan Syarif Hasyim Riau Province. The method used in this research is purposive sampling method. Data analysis using the Important Index Value (IIV) and Shannon-Wiener Diversity Index (H’). The result showed that the composition of tree species found in Undisturbance forest at Tahura Sultan Syarif Hasyim are 69 species from 24 family. The most dominant family are Myrtaceae and Dipterocarpaceae. The value of diversity in the type of tree level is 3,86. The diversity of tree species in Undisturbance forest at Tahura Sultan Syarif Hasyim Riau Province reach level of high with value belongs to H’>3. The tree species that have highest important value index is meranti pirang (Shorea leprosula) and Litsea spenTree compositionDiversity of speciesUndisturbance forestTahura Sultan Syarif HasyimArticle