Abstract: To provide a theoretical basis for research and development of compound bacteria agent PB12, the biocontrol ability and the growth-promoting effect of PB12 against Phytophthora blight of cucumber, as well as the impact on soil enzyme activity in the rhizosphere of cucumber, were analyzed. Growth index, incidence of Phytophthora blight cucumber, antioxidant enzyme activities of cucumber and the soil enzyme activity were measured by watering cucumber seedling with PB12 in greenhouse and field trials. The result showed that biocontrol efficiency of PB12 against Phytophthora blight of cucumber reached to 72.7% in greenhouse pot experiments. The activities of peroxidase (POD) and catalase (CAT) increased, and growth of cucumber seedlings was significantly promoted. Stem diameter, plant height, fresh weight and leaf area increased by 36.4%, 65.3%, 80.0% and 42.3%, respectively. The content of chlorophyll and root activity of cucumber seeding was remarkably increased. The activities of protease, invertase, cellulose and urease in rhizospheric soil of cucumber increased by 15.3%, 23.7%, 23.5% and 24.3% respectively, after 21 d of treatment with PB12. In 2012, the biocontrol efficiency of PB12 for Phytophthora blight of cucumber was 68.8%, and cucumber production increased by 38.1% in field experiments. PB12 can effectively control the cucumber blight, promote cucumber seedlings growth and improve soil enzyme activities in the rhizosphere of cucumber.