Abstract: In order to improve the fermentation process of vegetables and study the effects of pickles old soup on the structure of prokaryotic microbial community. The 16S rDNA V3 gene fragment of the fermented cabbage system was isolated by means of polymerase chain reaction combined with denaturing gradient gel electrophoresis(PCR-DGGE). Used Quantity One software to analysis the Shannon-Wiener diversity index of the prokaryotic microorganism,principal component analysis and similarity cluster analysis. The results showed that the number of microorganism in new soup was more than the old soup. The change rule of Shannon-Wiener index in the new soup was low-high-lower with the fermentation time,the change rule of Shannon-Wiener index in the old soup was high-low-higher with the fermentation time. The analysis of principal component showed that cabbage soup would come together in 1~8 d. In addition to the first day,the other days of the new soup also came together. The clustering map showed the microbial communities of new soup in 8 d was similar to the old soup in 1~8 d,which indicated that the prokaryotic microbial community structure in old soup was relatively stable than that of the new soup,the process of fermentation used the fermented vegetables pickled cabbage soup would better.