In order to study the effects of plant growth promoting rhizobacteria HG28-5 on cucumber growth and its rhizosphere microecology，this experiment sowed the cucumber seeds in trays after soaking them in HG28- 5 suspension．Then the quotas of emerging and seedling growth were examined to confirm its promotion effects on cucumber growth．The enzymatic activities in rhizosphere soil，available N，P，K and microbial population were measured to omprehend the effects of HG28-5 on cucumber rhizosphere soil microecology，and to check the colonization densities of HG28-5 in cucumber root and its rhizosphere soil in seedling stage．The results showed that soaking seed in HG28-5 treatment could remarkably increase seedling emergence potential，germination index and improve germination uniformity of cucumber．The soaking treatment with HG28-5 could also remarkably increase the plant height，numbers of leaves，root length，shoot fresh weight and root fresh weight of cucumber during its seedling stage，and significantly improve cucumber root system activity．The soaking treatment with HG28-5 could remarkably improve urease，phosphatase and sucrase activities in cucumber rhizosphere soil，increase the available P content，the amount of bacteria and antinomycetes，While decreaseing the rhizosphere soil fungi quantity during its seeding stage．Besides，HG28-5 could colonize well in cucumber rhizophere．Thirty days after sowing，HG28-5 could maintain a density of 9.20×10⁵ cfu · g^-1 and 5.90×10⁵ cfu·g^-1，respectively in cucumber root and its rhizosphere soil．