This study aims at elucidating the growth-promoting effects and biological function of Bacillus velezensis BMF03 strain on cucumber seedlings. A pot trial was conducted using different approaches such as soaking seed,mixing soil, filling root and mixing soil with fermented bran residues. Treatment of cucumber seeds, soil and seedlings with different concentrations of BMF03 fermentation liquid and fermented bran. The plant height, stem diameter, fresh weight and dry weight were measured. The plate-incubation method and colorimetric method were used to determine the abilities of strain BMF03 on fixing nitrogen, solubilizing phosphate and potassium, producing indoleacetic acid, iron carrier and ACC deaminase. The results showed that BMF03 fermentation liquid and bran fermentation have obvious promoting effects on the growth of cucumber seedlings by different treatment methods. The most effective treatment method was the soil-mixing treatment with fermented bran, the second is the treatment of fermentation liquid mixed with soil. Strain BMF03 could fix nitrogen and produce ACC deaminase, indole acetic acid and iron carrier. The relative content of iron carrier was up to 24.65%, the maximum amount of indole acetic acid was 2.8 mg/L. Bacillus velezensis BMF03 does not have the function of dissolving phosphorus and potassium.