The microbial community of normal and swollen canned soy sauce was investigated using molecular biological method. The PCR-denaturing gradient gel electrophoresis (DGGE) profiles showed that four lactic acid bacteria (LAB), including Lactobacillus acidipiscis, L. pobuzihii, L. piscium and another Lactobacillus sp., were involved in the swollen canned samples. Plate technique showed that three diverse species of Bacillus (B. subtilis, B. oleronius and B. flexus) were present in the swollen canned samples. However, much less bacterial contaminants were detected in the normal samples. According to the HPLC analysis, the lactic acid concentrations of the swollen canned samples were significantly higher than those in the normal samples. These results indicated that LAB can play a key role in contributing to the acidisation of the swollen canned soy sauce products. Our results confirmed the existence of Bacillus sp. and LAB in the packaged fermented soy sauce.