In order to investigate the correlation between the transcriptionally active Clostridia and the volatile organic acids metabolism in the fermented grains for the production of Chinese strong flavor Baijiu (CSFB), the methods of macrotranscriptomics and gas chromatography-mass spectrometry were used to determine the composition, succession, function of active Clostridia, and types of organic acids in fermented grains of CSFB. The results showed that there were 6 orders, 27 families, 148 genera assigned into Clostridia detected, and Heliobacteriaceae was dominat bacteria at the family level. The average relative abundance of clostridial community reached highest level at 15th day for the fermentation. The whole fermentation process could be divided into three phases according to the abundance variation of clostridial community, early fermentation (3-7d), middle fermentation (7-25d), and late fermentation (25-60d). Various degrees of correlations had been observed between the top 10 genera and eight volatile organic acids, such as acetic acid, butyric acid, caproic acid and etc.. The KEGG functional annotation indicated that Clostridia was mainly involved in carbohydrate metabolism, translation, and energy metabolism. The synthesis pathway of acetic acid and butyric acid involved 25 genes and 22 carbohydrate enzymes from 12 identifiable genera and unidentified genera, and their related genes had the highest expression level at 45th day for the fermentation, with Clostridium was the main contributor. This study aimed to provide basic data and theoretical support for further revealing the solid-state brewing mechanism of CSFB, and help clarify the composition and function of active clostridial communities in the complex microecosystem of fermented grains for the production of CSFB.