In aim to identify the gas characteristics produced by different species of yeasts and their influence on fermented dough acidity, the curves of gas production, under the condition of 28, 32, 35,38 and 40 ℃, were determined respectively. The acidity and pH value of dough during fermentation were determined as well. Results showed that the optimum temperature for gas production was 38 ℃. The gas properties of dough, fermented by different yeasts, were obviously different. The acidity and pH value of dough was relevant to both adding amount of yeast and sugar resistant characteristics of yeast. The acidity was increasing during fermentation process, thus the pH value declined.