The objective of this study was to compare the diversity of the cultivable bacteria with the diversity of the total bacterial population in soil. Two 16S rDNA libraries, library a and library b, were constructed with DNA extracted directly from soil and cultivable bacteria derived from red soil in Jiangxi. About 100 positive clones selected randomly from each library were investigated by ARDRA (amplified rDNA restriction analysis). After PCR amplification of insert fragments, restricted digestion of the PCR products were carried out with two restriction enzymes, namely Hha and Rsa. The statistic data showed that, Shannon-Wienner index, Simpson index, Richness and Evenness of library a were 4.432, 0.987, 18.885 and 0.973, and all of them were higher than those of the counterparts of library b which were 2.271, 0.758, 5.736 and 0.501. It indicated that traditional cultivation methods have its limitations and difficulties in exploring the diversity and potential of microbial communities. But associate with the new molecular technology, we can analyze the diversity of the microorganism community, evaluate the ecology environment and exploit the microorganism gene resources.