In this study, the effects of ultrasonic treatment (UT) at different powers (0, 120, 180, 240, 300, 360, and 420 W) for different durations (0, 3, 6, 9, 12, 15, and 18 min) and/or addition of purple sweet potato dietary fiber (PPDF) at different levels (0%, 1%, 2%, 3%, 4%, and 5%; m/m) on the gel properties of chicken breast myofibrillar protein (MP) were investigated. The results showed that the loss modulus (G’), storage modulus (G”), active sulfhydryl group content, surface hydrophobicity, water-holding capacity, gel strength, and textural properties increased first and then decreased with the increase in ultrasonic power, time and PPDF addition. The best gel characteristics of MP were obtained through UT for 9 min at a power of 360 W combined with addition of 4% PPDF. Both UT and addition of PPDF improved the gel properties of MP, and their combination was more effective than either alone.