In order to shorten the period and raise the efficiency of the feces and sewage treatment, alkali proteinase was used and then the ingredients of night soil was examined. The activity of alkali proteinase still remained in sewage after 4 days. When night soil was treated with alkali proteinase, BOD and fatty acids increased, and organic nitrogen changed to ammonium nitrogen. A large amount of amino acid was detected on the first day, but almost none of amino acids was detected on the fourth day. The experiment to certify the constituents of organic substances which increase BOD carried out using gel filtration with Sephadex G-15 showed that the peak of fatty acid coincided with that of BOD. Approximately 69% of BOD after treatment with alkali proteinase was found to be attributable to fatty acids. The feces and sewage treatment with alkali proteinase was found to be available to shorten the period and raise the efficiency of treatment.