【Objective】 The aim is to evaluate the growth promoting ability of Streptomyces zaomyceticus Sz-11 and its biocontrol potential against rice bacterial leaf streak disease, and to explore its preliminary bacteriostatic mechanism. 【Methods】 The antibacterial spectra of Sz-11 against seven plant pathogenic bacteria and 11 plant pathogenic fungi were determined by Oxford cup method. The growth promoting potential of Sz-11 was evaluated in a seed soaking experiment and irrigation experiment. SDS-polyacrylamide gel electrophoresis (SDS-PAGE), agarose gel electrophoresis (AGE), confocal laser scanning microscope (CLSM), scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FTIR) were used to analyze the effects of the active products in fermentation liquor on Xooc protein expression, genomic DNA synthesis, cell membrane permeability, cell morphology, cell membrane surface material structure and composition. The biocontrol potential of Sz-11 against rice bacterial leaf streak (BLS) disease was studied in a potted experiment.【Results】 Sz-11 showed good antagonistic activity against Pseudomonas syringae pv. tomato, Fusarium oxysporum f. sp. momordicae, Colletotrichum orbiculare, Alternaria alternata and other plant pathogens, and had outstanding antagonistic activity against Xanthomonas oryzae (Xoo and Xooc). Sz-11 can promote the germination and growth of rice seeds, shorten the germination cycle, which can also accelerate the accumulation of organic matter and root differentiation in the vegetative growth stage of rice. Sz-11 can affect Xooc protein expression, change cell membrane permeability and membrane surface material composition, resulting in cell swelling, deformation and death, but does not affect Xooc genome DNA synthesis. The relative control effect of Sz-11 on BLS of four rice varieties ranged from 65.63% to 84.38%, and the prevention effect in advance was better than the post-infection treatment as revealed in a pot experiment. 【Conclusion】 Sz-11, with a broad antibacterial spectrum, is a beneficial plant growth promoting rhizobacteria. By functions on the cell membrane and hampering protein synthesis of Xooc, it inhibits the growth and reproduction of pathogenic bacteria, thereby effectively preventing the occurrence of rice bacterial leaf streak disease. Thus, the information listed in this article shows that Sz-11 has utilization potential in biological control.