Abstract: The paper aims to explore the growth promotion and disease control effects of Bacillus subtilis strain NKG-1 on tomato powdery mildew. The effects of NKG-1 fermentation broth with different microbial density on growth promoting by irrigation were studied. And the preventive and treatment effects of NKG-1 on tomato powdery mildew by spray were analyzed. Potted tomatoe test showed that: the most effective microbial density was between 1×107cfu/mL to 1×109cfu/mL, under which the seedling fresh weight increased by 35.62% and the root length increased by 55.01% compared with the control. The greenhouse growth promotion test showed that: the number of fruit set was 28.57% higher than that of the control, and the crown width increased by 16.72%. Furthermore, the greenhouse disease control test showed that: the preventive effect of sprayed NKG- 1 fermentation broth to tomatoes before powdery mildew onset was 87.55%, the treatment effect on tomato after powdery mildew onset was 47.74%. These results indicate that NKG- 1 has a significant effect on growth promotion and disease control of tomatoes, and the preventive effect of powdery mildew is better than that of treatment. This study provides a theoretical basis for the large-scale application of NKG-1 to tomatoes.