We formulated a method for preparing low-salt fish sauce using soy sauce yeast. In 10% NaCl fish sauce mash, to which 5 % ethanol was added, bacterial growth was nearly 10² colony forming units (cfu) / g throughout the fermentation period ; in fish sauce mash without ethanol, the bacterial population markedly increased beyond 10⁸cfu/ g in the first 10 days of fermentation. To prepare the low-salt fish sauce, we isolated the A-9 strain of the yeast Zygosaccharomyces rouxii from soy sauce mash ; 10⁶cells/ g of the strain was added to fish with 10% glucose or 22% wheat koji as the carbon source for alcohol fermentation to prepare a 10% NaCl fish sauce mash. In the mash, yeast produced alcohol as they grew, which inhibited the growth of bacteria. Fermentation was complete in 60 days, and the mixture was pressed to obtain liquid. The low-salt fish sauce prepared with high levels of yeast in this study had a half concentration of NaCl and a more favorable fermented flavor than commercial fish sauces made in the traditional manner.