Abstract: This study conducted cooperative treatment involving germination and fermentation of naked oats to enhance the bioaccessibility of total phenolics. The effects of this collaborative treatment on the bioaccessibility of total phenolics and antioxidant activities in naked oats were investigated using simulated digestion and colon fermentation models in vitro. The results showed that the total phenolic content, DPPH free radical scavenging rate, reducing power and hydroxyl free radical scavenging rate of naked oat treated by germination and fermentation were 106, 6.79, 2.56 and 2.98 times of the control, respectively. During the simulated digestion process, the bioaccessibility of total phenolics in the oral, gastric, and intestinal stages was found to be 2.4, 2.5, and 2.3 times higher than that of control oats, respectively. Additionally, the bioaccessibility of hydroxyl radicals was observed to be 16.0%, 10.4%, and 0.52% greater than that of control naked oats. Furthermore, the bioaccessibility of DPPH free radicals was found to be 46.1%, 53.44%, and 61.81% higher than that of control oats, respectively. The bioaccessibility of reduction power was also significantly increased, with values 45.19%, 92.63%, and 118.54% higher than that of the control sample. During the colonic fermentation stage, the bioaccessibility of total phenolics in fermented naked oat at 24 hours was found to be 1.84 times higher than that of the control sample. Furthermore, in addition to hydroxyl radical bioaccessibility, the antioxidant bioaccessibility of naked oat subjected to collaborative treatment was also higher compared to the control sample. These findings suggest that the combined treatment of germination and fermentation of naked oats not only enhances the bioaccessibility of total polyphenols in the digestive tract, but also improves their bioaccessibility in the colon. The results of this study provide a theoretical basis for the processing of naked oats and the development of functional food.