Abstract: Lactic acid bacteria (LAB) are commonly used as fermentation strains or probiotics in food. The main application form of LAB in the industry is freeze-dried powder. During freeze-drying, formation of ice crystals and dehydration could damage LAB cells, resulting in decreased metabolic activity or even cell death. The viable count or fermentation activity are important quality indices of the freeze-dried powder for lactic acid bacteria. At present, viability derived freeze-drying stress response mechanisms and survival improvement technology are gained widespread attention. In this study, the factors affecting fermentation activity in freeze-drying process are reviewed. And the effects and mechanisms of cell membrane fluidity, permeability, and heterogeneity of cell membrane damage on the fermentation activity during the freeze-drying were expounded. The study provides a basis for the further clarifying mechanism of freeze-drying affecting the fermentation activity of LAB. It also promotes the development of freeze-drying technique for LAB.