Abstract: The effects of constant temperature and oscillatory temperature on the properties of low-salt fish sauce prepared from mackerel (decapterus maruadsi) by adding koji were investigated. When fish sauce was prepared at constant temperature of 20℃ or 40℃, the pH of fish sauce mash was remained at 5. 2 ~ 5. 5 during fermentation. On the other hand, the pH of fish sauce mash reached up to 6 during 90 days of fermentation at 30℃, resulting in highest total volatile basic nitrogen content (TVB-N) of fish sauce production, suggesting that 30℃ was not suitable for preparing low-salt fish sauce fermented by adding koji. However, the lower amino-acid nitrogen content (AA-N) and total soluble nitrogen content (TS-N) were observed in the fish sauce production prepared at 20℃, while a slight bitterness was found in that of 40℃. When the fermentation temperature was controlled at 20℃ in the initial 30 days of fermentation stage, 30℃ in the 30 days of second stage, 40℃ in the 30 days of last stage, not only the AA-N and TS-N of fish sauce production were increased, but also the TVB-N of fish sauce production was decreased. Based on the analysis of free amino acid compositions and sensory evaluation, it was revealed that the quality of fish sauce production could also be improved by the subsection fermentation process.