Soil microbial diversity reflects the degree of soil ecosystem health, plays an important role in soil nutrient cycling, and largely affects the forest land productivity. Using the rhizosphere and bulk soils from poplar plantations, extracting the genome DNA of total microorganism by MOBIO PowerSoil DNA Isolation Kit, the DNA extraction and amplification of 16S rDNA V3 area of microbes were studied in this paper to study the effect of plantation longterm management on soil microbial diversity. The results showed that this method can extract genome DNA of total microorganism from 6 kinds of soils from poplar plantation. The genomic DNA fragments was more than 2 000bp and the electrophoresis bands of DNA were clear, complete and without obvious degradation, and the genome DNA could be the favorable templates of 16S rDNA PCR amplification of soil bacteria. The brightness of 6 genomic DNA electrophoresis bands in electrophoresis figure is different, of which the DNA band of rhizosphere soil(B3)from first generation poplar plantation was the most bright, while the one of bulk soil(FB18)from third generation plantation was the most dark. According to the concentration detection of different DNA samples, the DNA concentration of B3 was about 69ng·ml-1, and that of FB18 was only 20ng·ml-1. Choosing 27F／1492R and F338GC／R518 primers, and using nested PCR strategy, this study successfully amplified the strip of 16S rDNA V3 area with about 220bp.