Abstract: This study aimed to explore the appropriate range of oat dietary fiber addition for reducing the degree of starch aging while ensuring the quality of the cake. This study investigated the effects of oat dietary fiber (0%, 3%, 6%, 9%, 12%, 15%) on the quality and anti-aging properties of fresh chiffon cake during storage. Multiple indicators, including batter density, specific volume, baking loss rate, moisture content, color, texture, and sensory evaluation, were analyzed. Advanced techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were employed to characterize the structural and functional changes. Results demonstrated that 3%~9% oat fiber addition effectively mitigated cake staling while preserving its essential quality attributes. After one week of storage, compared to the sample with no additions, there was a decrease in the core enthalpy value and relative crystallinity of the cake added with oat fiber, indicating a reduction in the degree of aging in the chiffon cake. When the addition amount was 9%, the lowest batter density of chiffon cake was 0.69 g/mL, the highest specific volume was 3.56 mL/g, the highest moisture content was 45.84%, and other quality indicators were excellent. According to a comprehensive comparison, the chiffon cake is of the best quality and shows anti-aging ability when the addition of oat fiber is 9%, which effectively improves the aging of chiffon cake during storage.