Abstract: To explore how rhizosphere microbes responded to environmental change in Populus tremula plantations in southeast Shandong Province. Seasonal dynamics and vertical distribution of rhizosphere microbe number and rhizosphere effect were investigated and compared it to the bulk soil by using plate count and conventional chemical methods, respectively. Additionally, the correlation between rhizosphere microorganism number and soil available nutrients were also studied. The results obtained were as follows: the seasonal dynamic patterns of bacteria, fungi, actinomycete and total microorganism were increase-decrease- increase-decrease, that was spring and autumn were higher than summer and winter. Bacteria, fungi, actinomycete and total microorganism reached the highest value in the middle of April, and the second peak appeared in October and minimum value occurred in December. The number of rhizosphere microbe was shown as bacteria＞actinomycetes＞fungi. The number of bacteria, actinomycetes and total microbe in rhizosphere increased with age, but the number of fungi decreased. In general, vertical distributions of bacteria, fungi, actinomycete and total microorganism reduced as the soil depth increased, except 0-10 cm. The rhizosphere effect (R/S) of bacteria, fungi, actinomycete and total microorganism was distinct. Furthermore, the rhizosphere effect showed unimodal peak with maximum value in August. The correlation between number of rhizosphere bacteria, fungi, actinomycete, total microorganism and soil hydrolyzable nitrogen, soil rapid available phosphorus were positive, respectively, and the correlation between number of rhizosphere microbes and soil organic matter were negative.