In this study, octenyl succinic anhydride (OSA)-modified millet starch was prepared from millet starch via ultrasonic pretreatment. The effects of starch particle concentration and oil-to-water ratio on the stability of Pickering emulsions were investigated, and the potential of Pickering emulsions as curcumin delivery carriers was evaluated through in vitro simulated digestion experiments. The results showed that with increasing starch particle concentration, the particle size of OSA-modified millet starch-stabilized Pickering emulsions decreased significantly (from 2051.67 to 720.83 nm), the emulsification index and apparent viscosity increased, and the stability improved, reaching a basically stable state at a concentration of 5 g/100 mL. In addition, with the increase in oil phase ratio, the particle size of emulsions increased (from 638.11 to 2967.35 nm), accompanied by corresponding improvements in the emulsification index, apparent viscosity and stability. In comparison to native starch-stabilized Pickering emulsion, the Pickering emulsion stabilized by OSA-modified millet starch exhibited higher curcumin loading capacity and in vitro bioaccessibility (90.38% and 23.49%, respectively) along with improved free fatty acid release and storage stability. Therefore, Pickering emulsions stabilized by OSA-modified millet starch are an effective carrier for protecting and delivering bioactive substances such as curcumin.