Abstract: A Bacillus altitudinis ST15 antagonizing Xanthomonas oryzae and use thereof, the Bacillus altitudinis ST15 was deposited in China General Microbiological Culture Collection Center on Jun. 28, 2020 and has the deposit number of CGMCC No. 20156. The Bacillus altitudinis has a relatively high antagonistic activity to Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola, can promote growth of rice and improve a drought resistance of a rice seedling, and has a relatively strong tolerance to common chemical microbicides for controlling bacterial diseases of rice. A bacterial suspension or a biocontrol inoculant prepared from this strain has a relatively high biocontrol effect on bacterial blight of rice and bacterial leaf streak of rice, can replace or reduce chemical pesticides, improves safety of food and ecological environment, and has relatively high economic and social benefits.