Abstract: The method of phospholipid fatty acid(PLFA)was used to study the microbial species and biomass of the medium and high temperature Daqu and the workshop air in different fermentation stages. The results showed that the number of PLFA species in each stage of Daqu was higher than the air. Moreover,the microbial species detected in the air were usually found in Daqu. The maximum bacterial biomass of two types of Daqu and their air was found in the fourth stage of fermentation. The bacterial biomass of medium temperature Daqu was 78.09 nmol/m³ and the high temperature Daqu was 103.62 nmol/m³. The bacterial biomass in the medium-temperature Daqu room air was 36.24 nmol/m³ and in the high temperature Daqu room air was 88.39 nmol/m³. The medium temperature Daqu was dominated by thermophilic dehydrogenophilus and Gram-negative bacteria in the whole fermentation process. Gram-positive and Gram-negative bacteria were dominated in the medium temperature Daqu room air. The high temperature Daqu was dominated by Gram-negative bacteria in first stage. The Gram-positive bacteria became dominant when the Daqu was entering the fermentation room. The air of high temperature Daqu room was dominated by Gram-negative bacteria during the fermentation process. Through principal component analysis,the results showed that the community composition of medium temperature Daqu was similar in the air of fermentation room in the pre-fermentation. The high temperature Daqu and its air of workshop were similar in the whole fermentation process except for the fourth stage of fermentation.