¹College of Animal Science and Technology, Shihezi University, 832003 Shihezi, Xinjiang, CHINA DOI : 10.9775/kvfd.2021.26965 In this study, we investigated the eff ects of diff erent litter sizes on the rate of uterine involution in Hu sheep. Using B-mode ultrasonography, we recorded changes in the uterine horn diameter and the maximum uterine caruncle diameter in 60 primiparous Hu sheep from days 0 to 45 postpartum. Th e uterine horn diameter decreased gradually postpartum from 79±1.42 mm at day 0 to 10.87±0.5 mm at day 45 with singleton parturition, from 91±6.58 mm at day 0 to 10.63±0.32 mm at day 45 with twin parturition, and from 107±3.67 mm at day 0 to 11±0.87 mm at day 45 with triplet parturition. Th e time to complete uterine involution postpartum was 30, 35 and 40 days postpartum in singleton, twin and triplet parturitions, respectively. (P<0.05). Th e maximum uterine caruncle diameter also decreased gradually from 12.43±0.91 mm at day 3 to 8.82±0.27 mm at day 10 with singleton parturition, from 12.14±1.19 mm at day 3 to 8.31±0.94 mm at day 10 with twin parturition, and from 12.5±0.66 mm at day 3 to 7.94±0.95 mm at day 10 with triplet parturition (P>0.05). Th us, diff erent litter sizes had a greater eff ect on postpartum uterine horn recovery than on the uterine caruncle. Furthermore, the rate of uterine involution in ewes with singleton parturition was significantly higher than that with triplet parturition. Our findings provide a reference for improving the reproductive performance of Hu sheep. Keywords : Hu sheep, Litter size, Uterine involution, Ultrasound