Abstract: In order to obtain yeast suitable for high-acid juice fermentation,two strains of yeast which grew well at pH2.3 were isolated and screened from the naturally fermented juice of blueberry and red raspberry,and their morphology,physiology,biochemistry and molecular biology were studied. Identificated the J-23 was Hanseniasporus guilliermondii,and the L-6 was Saccharomyces cerevisiae. The acid-tolerant adaptability of J-23 and L-6 yeasts were studied in a pH2.3,pH4.8 acid environment using commercially available fruit wine yeast and Hanseniaspora uvarum as control strains. And the cell membrane,cell wall and intracellular structure were observed by SEM and TEM. The activities of catalase(CAT)and superoxide dismutase(SOD)in acid stress were measured. The results showed that the morphology of J-23 and L-6 yeast cells had no obvious depressions,wrinkles and so on,the cell structure was clear,and the vacuole became large. The SOD activity of J-23 yeast and control bacteria 1,L-6 yeast and control bacteria 2 were respectively 790.98,768.71,795.02 and 772.15 U/mL,meanwhile,the CAT enzyme activities were respectively 389.81,370.85,385.17 and 373.31 U/mL at pH2.3. The enzyme activities of both J-23 and L-6 strains were significantly higher than the control strains,which could better adapt to the acid stress environment.