Abstract: This research was to study the effects of disease prevention, growth promotion and defense enzymes induction of Bacillus mojavensis ZA1 on potato, and provide a theoretical basis for microbial fungicide and fertilizer use. The abilities of IAA secretion, nitrogen fixation, phosphate solubilization and inhibition enzyme production of ZA1 have been researched qualitatively by general methods. The effects of controlling disease and growth promotion of ZA1 on potatoes were studied under the condition of indoors and fields. The concentration of IAA secreted by ZA1 in the King medium with and without tryptophan were 12.17 and 9.75 mg/L. ZA1 possessed the capacity of nitrogen fixation and extracellular proteases, chitinase and glucanase production, but without the ability of phosphate solubilization. The control efficiency of ZA1 was 85.9% by spraying 10 times diluting fermentation broth on potato tubes in storage-period against potato gangrene, and was 26.56% by seed dressing fermentation broth with diluting for 20 times on potato tubes under field condition against potato late blight. In field condition, the production ratios of commodity potato were increased by 36.29% and 33.88% per hectare, respectively. Pot experiments with the seed dressing potatoes showed that the content of roots, stems and chlorophyll were higher than the control group. After treatment by ZA1 20 times fermentation broth on potato tubes, the length of the root and wet and dry weight were increased by 8 cm, 0.75 g and 5.07 g, respectively. In the same time, the plant height, stem diameter, stem wet and dry weight and the content of chlorophyll were increased by 2.74 cm, 0.27 cm, 0.52 g, 5.73 g and 0.54 mg/g, respectively. The root-shoot ratios of wet and dry weight were increased by 0.214 and 0.094, respectively. When spraying diluting fermentation broth of ZA1 on potato leaves, the results indicated that the activity of catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonialyase (PAL), SOD and POD of potatoes were increased. ZA1 possessed the biological function of disease prevention and growth promotion under indoor and field conditions obviously, which showed that ZA1 had the potential to become microbial fungicide and fertilizer.