This paper aimed to analyze the correlation of microbial community structural changes with its physicochemical properties in fermented substrates of the light flavour baijiu. The microbial composition， and correlation between community succession and physicochemical properties in the traditional fermentation process of light flavour baijiu was analyzed. 10 groups of light flavour baijiu fermented substrates were sampled every two days for 28 d (0， 2， 4， 6， 8， 12， 16， 20， 24， 28 d) by traditional batch fermentation. The composition of fungi and bacteria， water content， acidity， pH value， starch content and other physicochemical properties were determined. During the fermentation of light flavour baijiu， bacteria detected were distributed in 18 phyla and fungi in 7 phyla. A total of 467 genera were detected， including 311 bacteria. It mainly included Lactobacillus， Pediococcus， Leuconostoc， Weissella， Pantoea， Akkermansia， Obesumbacterium， Streptococcus with Lactobacillus and Pediococcus dominated. There were 156 fungal genera， including Kazachstania， Saccharomyces， Kurtzmaniella， Thermoascus， Aspergillu， Wickerhamomyces， etc.， where Kazachstania and Saccharomyces were dominant. The microbial composition in different fermentation containers was slightly different during the same period. The correlation analysis between microbial diversity and physicochemical properties in fermented substrates showed that the bacterial diversity was strongly and positively correlated with fermentation temperature and pH value， but negatively correlated with water and alcohol content. At the same time， fungal diversity in fermented substrates was not significantly correlated with physicochemical properties.