The quality of Pit-mud (PM) has an important influence on the fermentation of Chinese strong-flavor Baijiu (CSFB). In general, the older the pit, the better the quality of the PM and the better the quality of CSFB. In recent years, researches focused on improving the quality of PM and promoting the maturity of PM have become a hot spot. Based on the logical sequence from basic theory to improvement and application researches, the PM microbial community structure, species function, and artificial PM improvement were reviewed in this article. In the time dimension, with the increase of pit age, the diversity of the PM prokaryotic community gradually increased, and gradually stabilized (maturation), while the diversity of the eukaryotic flora gradually decreased, or even disappeared. In terms of spatial distribution, the diversity of bottom PM prokaryotic flora was greater than that of the wall PM. On the contrary, eukaryotes in PM tend to disappear at the bottom of the old pit. Some species in PM were found to be involved in caproic acid synthesis, such as Clostridium kluyveri and Ruminococcaceae CPB6. As PM matured, the PM flora gradually formed a complete metabolic network. The artificial PM can be effectively used to promote the maturation of PM. Through this review, new ideas were provided for further theoretical and application researches.