Abstract: To investigate the effects of different brine and fermentation methods on the quality characteristics of fermented chili peppers, this study employed four different fermentation methods: Natural fermentation with sterile water, co-inoculation fermentation (Lactiplantibacillus plantarum KUST-D1303:Pichia manshurica KUST-F1705=1:1) with sterile water, natural fermentation with aged brine, and co-inoculation fermentation with aged brine. The quality characteristics of the fermented chili peppers were compared and analyzed. Results showed that, compared to other fermentation methods, co-inoculation fermentation with aged brine significantly (P<0.05) increased the number of lactic acid bacteria, organic acid content, and the variety and concentration of volatile flavor compounds, especially alcohols, terpenes, and sulfur-containing compounds, while reducing nitrite content. Additionally, the pH of fermented chili peppers by co-inoculation with aged brine decreased rapidly and remained stable, which helped delay the yellowing and softening of chili peppers during fermentation. In conclusion, co-inoculation fermentation with aged brine can enhance the safety, flavor profile, and taste of fermented chili peppers, making it the optimal process for fermented chili peppers.