Sichuan Shai vinegar, a distinctive condiment from Southwest China, is produced through open-air solid-state fermentation, employing a unique Chinese herbal medicine mixture (Yaoqu) as the fermentation starter. Despite its culinary significance, the dynamics and roles of fungal communities within the Cupei fermentation phase remain understudied. This study employed high-performance liquid chromatography (HPLC) to quantify 11 organic acids and 17 amino acids, revealing a significant increase in organic acid content from 2.56 g/100 g-17.47 g/100 g dry weight and a gradual elevation in free amino acid content from 0.53 g/100 g-5.59 g/100 g throughout the fermentation process. Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) identified 85 volatile flavor compounds, predominantly consisting of 2 alcohols, 10 acids, 29 esters, 4 ketones, 6 aldehydes, and 14 other types. High-throughput sequencing facilitated the identification of key microorganisms, with Lichtheimia, Brettanomyces, Pichia, Saccharomyces, Kazachstania, and Syncephalastrum emerging as the most abundant fungal genera. Correlation analysis revealed significant positive correlations between 20 fungi and 11 organic acids, 24 fungi and 16 amino acids, and 50 fungi and 76 volatile flavor compounds. Notably, Lichtheimia, Pichia, and Brettanomyces were identified as the most influential in flavor metabolism. These findings elucidate the microbial metabolic mechanisms during Sichuan Shai vinegar fermentation, laying a foundation for further research and potential applications in vinegar production.