This research reveals how Sichuan-style black soybean soy sauce develops its distinctive complex flavor over six months of natural fermentation. The study tracked changes in taste and aroma compounds, identifying key flavor contributors like methional (sauce-like) and 1-octen-3-ol (mushroom-like). Different microorganisms dominate at different fermentation stages, with early-stage fungi breaking down proteins and later-stage bacteria and yeasts creating aromatic compounds. The findings provide insights for improving traditional soy sauce production methods.