We explored whether ultrasound treatment affected digestibility of myofibrillar protein (MP) isolated from modified atmosphere packed (MAP, 70% N and 30% CO) pork. MP digestibility under pepsin and pancreatin treatments decreased significantly with storage time. Ultrasound treatment increased the digestibility and produced a greater number of smaller peptides. However, the total peptide count and unique peptide counts were significantly reduced. Moreover, active sulfhydryl, total sulfhydryl, particle size, turbidity and surface hydrophobicity of MP increased with time, while protein solubility and ATPase activity decreased. Compared with the untreated samples, ultrasound treatment increased protein solubility, surface hydrophobicity, and active sulfhydryl content, but decreased total sulfhydryl content (except 10 d), particle sizes, turbidity and ATPase activity. Ultrasound treatment resulted in a decline in β-turn and α-helix contents. Therefore, ultrasound is conducive to the digestion. Additionally, structural and functional properties of protein in MAP were less stable than those in vacuum-packed pork reported before.