Abstract:[Objective] The aim of this study was to identify the culturable endophytic bacteria recovered from the Populus euphratica at the disused (122 years ago) ancient Ugan river of middle reachs of Tarim river, and to understand their Phylogenetic diversity and community structure. [Methods] Bacteria were isolated from the storage liquid in the stem of 2 Populus euphratica stands by using 3 types of different cultural medium (Luria -Bertani,Trypticase Soy Agar and Nutrient Agar), followed carry out 16S rDNA identifications and analysis of their biodiversity.[Results] A total of 62 phenotypically different isolates were sequenced and according to their 16S rDNA sequence similarities to type strains of described organisms,they have been placed into four phylogenetic groups (Firmicutes , Gamma Proteobacteria, Actinobacteria and Alpha Proteobacteria) , 18 genera (Bacillus,Pseudomonas,Kocuria,Staphylococcus,Oceanobacillus,Micrococcus,Planomicrobium,Planococcus,Brevibacterium,Pantoea,Macrococcus,Providencia,Halomonas,Rhizobium,Photobacterium,Psychrobacter,Brenneria and Acinetobacter), and 32 species . Among them, Bacillus and pseudomonas were the most widely distributed and predominant ,occupied the majority of isolates 40.32% and 16.13%, respectively. Isolate KTH-63 (HM371419) formed a distinct clade with Macrococcus brunensis in phylogenetic tree based on 16S rDNA sequence among the family Staphylococcaceae ,so it was demonstrated that the KTH-63 represents a potential novel genus and novel species within the family Staphylococcaceae with 92.491％ sequence similarity with the described species Macrococcus brunensis of this family . Isolates KLH-1,KLH-21,KLH-18, KLH-25,KNA-3,KTH-8,KTH-14,KTH-20 and KNA-26 with 96.089%-97.769% sequence similarities to their closely related members were presumed to be potential novel species, and the discovery rate of potential novel species in the endophytic bacterial community of Populus euphratica was reach up to 16.13%. Furthermore ,10 genera(1 potential novel genus and 9 known genera as the plant endophytic bacteria firstly discovered in Populus euphratica stands ) and 18 species (10 potential novel species and 8 known species as the plant endophytic bacteria firstly discovered in Populus euphratica stands) have been added to the plant endophytic bacterial categoria by the data obtained in this work. [Conclusion] The result showed that the cultivable endophytic bacterial diversity in Populus euphratica at Ugan riwer was very abundant and have high percentage of potential novel species, and it have greatly refreshed the plant endophytic bacterial records .The community structure obtained in this study also may be presumed as a miniature of the endophytic bacterial flora in the Populus euphratica during the recent ages before the affect of modern civilization prossessing to Tarim river valley,which deserve further study and exploitation.