Abstract: Aiming at the frequent occurrence and difficult prevention of crabapple branch diseases in the Summer Palace, the effects of micro-ecological regulation on growth promotion and disease resistance of Malus × micromalus Makino were clarified through forest experiments. The results showed that from 2013 to 2015, the control effect of Cytospora canker was maintained at 53.11%−60.05% on 20-year-old trees. The branches thickened by 11.80%−21.01%, the chlorophyll content increased by 32.70%−37.04%, the leaf weight increased by 19.02%−27.59%, and the deciduous and yellow leaves decreased by more than 10%. From 2014 to 2023, we began to apply micro-ecological regulation technology to the 30-year-old Malus × micromalus Makino along the corridor of the Summer Palace, and set up control groups. The growth and disease occurrence were investigated in the current year, the second year and the tenth year. The results showed that after two years of continuous application of micro-ecological agents, the disease prevention effect of Cytospora canker reached 59.22%, the disease prevention effect of Botryosphaeria canker was 26.37%, the chlorophyll content increased by 25.49%, and the leaf weight increased by 21.34%. After 10 years of continuous application of micro-ecological agents, the disease prevention effect of Cytospora canker reached 68.50%, the disease prevention effect of Botryosphaeria canker reached 53.53%, the chlorophyll content increased by 39.50%, and the leaf weight increased by 26.71%. The micro-ecological regulation technology has a significant effect on promoting growth and disease prevention, which can effectively improve the tree vigor and prolong the leaf holding period.