This experiment was conducted during the two seasons of 2021/ 2022 and 2022/ 2023 at the faculty of agriculture and Natural Resources private, Aswan University, Aswan governorate, Egypt to isolate and characterize some endophytic bacteria from Salvadora persica roots and study their effects on the plant growth, yield and chemical compositions of onion plants. Freshly roots of S. persica were collected from tree grown in Al-Gaafra village, Daraw, Aswan governorate. Two bacterial endophytic were isolated and the 1^st isolate was identified as Bacillus subtilis and the 2^nd isolate SEndo 2 (it will be identified later). Numbers of endophytic bacteria were isolated, identified, and tested for their ability to plant growth promotion. Out of 8 clones 2 clones (Bacillus subtilis and SEndo 2) were identified based on their good plant growth promotion for different tests, for phosphate solubilization, nitrogen fixation, Gram typing of bacteria, motility, and IAA production. The two isolates successfully produced indole acetic acid in quantities ranged from 1.4 to 2.1 µg·mL⁻¹.  Two bacterial isolates of SEndo 2 (Gram-negative bacteria), Bacillus subtilis (Gram-positive bacteria) were screened for plant growth-promoting activities revealing that the isolates showed production of IAA, and capacities to solubilize phosphate, but only Bacillus subtilis was able to fix nitrogen and fix nitrogen. The field experiment investigated the effect of two isolated which were selected to study of the influence inoculation endophytic bacteria on the growth and productivity of onion plants. A field trial as randomized complete-blocks (RCB) with 4 replicates in the two seasons was carried out in the farm of Faculty of Agriculture and Natural to investigate the response of onion crop (cv. improved Giza 6) to inoculation with individual and composite inoculums of plant growth-promoting bacteria. Onion inoculation treatments showed a significant effect on the growth, productivity and chemical compositions during the two seasons. The effect of different inoculation treatments can be arranged in descending order on increasing onion plant height as follows: mix of SEndo 2 and Bacillus subtilis > Bacillus subtilis > SEndo 2> control in the different periods for both seasons.