[Objective] This study aims to compare the flavor substances in Maotai-flavor Daqu samples with different sensory characteristics, explore their correlations with free amino acids and bacterial community composition, and preliminarily analyze the reasons for the flavor formation of Maotai-flavor Daqu. [Method]The flavor substances, free amino acids, and bacterial community composition in Maotai-flavor Daqu samples with different sensory characteristics were analyzed by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry and quantitative analysis of multi-components by a single marker (UPLC-HRMS-QAMS), and high-throughput sequencing, respectively. The effects of different free amino acids and bacterial community composition on the flavor of Maotai-flavor Daqu were analyzed. [Result]A total of 75 flavor substances and 14 free amino acids were identified in Maotai-flavor Daqu, of which the flavor substances were mainly pyrazines, alcohols, esters, acids, and aldehydes. Yellow and black Daqu had similar flavor substances, with greater differences from white Daqu. The mass fraction of free amino acids ranged from 3.76 to 9.22 mg/g, with bitter amino acids being dominant, and the mass fraction of free amino acids in Qupi was higher than that in Quxin. The correlation analysis showed that multiple free amino acids such as lysine, tyrosine, tryptophan, and citrulline were closely related to the metabolism and synthesis of pyrazines, esters, acids, and aldehydes. Kroppenstedtia was the characteristic bacterial genus of yellow Qupi (YP) samples, and it was closely related to the metabolism and synthesis of esters such as ethyl lactate and ethyl phenylacetate. Pseudomonas was the characteristic bacterial genus of yellow Quxin (YX), black Qupi (BP), and black Quxin (BX) samples, and it had significantly positive correlations with aldehydes such as 5-methyl-2-phenyl-2-hexenal, benzaldehyde, and 2-phenyl-2-butenal. The main bacterial genera of white Qupi (WP) and white Quxin (WX) samples were Blastococcus and Scopulibacillus, respectively, which had significantly negative correlations with ethyl lactate, 2-phenyl-2-butenal, and 5-methyl-2-phenyl-2-hexenal. [Conclusion]The flavor substances vary in Maotai-flavor Daqu samples with different sensory characteristics, and the investigation in this field could further reveal the formation mechanism of Maotai-flavor Daqu.