Abstract: The dynamic change patterns and differences of the microbe counts, pH, total acid, color difference, nitrite, reducing sugar, organic acid, and volatile flavor substances during fermentation were analyzed using fermented radish without the addition of red yeast rice (RYR) as a control in order to examine the impact of RYR on the quality of fermented radish. The findings demonstrated that the total acid content was significantly higher, and the pH of fermented radish with RYR decreased more rapidly compared to the control group. After adding RYR, the fermentation group exhibited a higher total organic acid content than the control group, with significantly greater amounts of acetic and lactic acid. Additionally, the total color difference value differed from that of the control group (P<0.05), and the addition of RYR turned the fermented radish red. In the two groups, 132 volatile flavor substances were detected, comprising 19 alcohols, 51 esters, 3 phenols, 6 ketones, 21 aldehydes, 4 ethers, and 28 other compounds. Twelve differential compounds (VIP value>1, P<0.05) were obtained by OPLS-DA analysis, including 3 alcohols, 8 esters, and 1 sulfide, among which the ester differential compounds contributing to the floral and fruity aroma flavor were relatively higher in the red yeast rice-added fermentation group. The results reveal that red yeast rice plays an important role in the quality and volatile flavor of fermented radish, and it is worthwhile to carry out more in-depth studies to facilitate the development and promotion of red vinasse acid.