Doenjang (fermented soybean paste) is one of the korean traditional fermented soybean product which is consumed with cooked rice as a soup or paste. During the fermentation, soybean protein hydrolyzed into amino acids and various peptide, and various organic acids by mirobes related and enzymes produced by meju fermentation. Some commercial products locationally samples give more sour taste than normal due to abnormal fermentation which the reasons are not clear. Three samples that gave sour taste organoleptically were collected and analyzed their characteristics such as pH, moisture content, acidity and microbial counts. The pH of the sour sample were lower than the normal with higher acidity as pH 5.39 (normal) to pH 4.36 (S2) and 15.80 ml of (0.1N NaOH consumed) to 21.80 ml (S1) respectively. Salt and moisture contents were different with sour and normal Doenjang as 16.38% (normal)to 8.92% (S3) in salt and 55.94% (normal) to 49.34% (S1) in moisture content. Total viable counts were 4.1 × 108(normal) to 8.0 × 105 (S2), and 3.4 × 108 (normal) to 8.0 × 105 (S2) in acid producing microbes at BCP plate. Yeast and mold were not detected. The composition of acids as mainly lactic acid and acetic acid of sour Doenjang. Total free amino acids content were lower the sour Doenjang than the normal.