Abstract: To improve the texture deterioration and whey separation problems of low-fat yogurt due to its low fat content and enhance its storage quality. In this study, the blueberry pulp dietary fiber (BPDF) was first modified by ultrasonic-assisted enzymatic method, and the optimal process was determined through single-factor and response surface optimization. Subsequently, the influence of different concentrations of modified BPDF on the storage quality of low-fat yogurt was explored. The results showed that under the conditions of ultrasonic power of 443 W, treatment time of 20 min, addition amount of compound enzyme of 2.5%, temperature of 60 ℃, and enzymatic hydrolysis time of 2.5 h, the yield of soluble dietary fiber (SDF) prepared was the highest, reaching 15.87%. Moreover, its water-holding capacity, oil-holding capacity, expansion capacity and swelling property were all significantly improved (P<0.05). Furthermore, the modified BPDF was applied to low-fat yogurt, which could significantly enhance the texture and rheological indicators such as hardness, cohesion, and storage modulus (G') of the product within a 28-day refrigeration period (P<0.05). Among them, the group with 2% modified BPDF addition performed the best throughout the storage period. Not only was the whey precipitation rate 29.72% lower than that of the control group at 28 days of storage, but also the antioxidant performance was higher (the DPPH free radical scavenging rate was always above 80%, and the ABTS⁺ free radical scavenging rate remained above 60%), and the sensory score ranked first among all groups. This study provides a new solution for improving the storage quality of low-fat yogurt and the high-value utilization of fruit residue.