Abstract: Omeisaurus jiaoi, a new species of giant sauropod is described in this paper. The specimen (ZDM 5050) was discovered from the Xiashaximiao Formation of the Middle Jurassic of Zigong Dinosaur National Geopark, Sichuan. ZDM 5050 is a nearly complete skeleton. Its main features can be summarized as follows: dorsal vertebrae are tall and large. The anterior dorsal vertebrae (dorsals 1 to 6) are opisthocoelous. The pleurocoels of the dorsal vertebrate are well developed except on the 1stdorsal. The neural spines are club-like and the neural spines of the anterior dorsal vertebrae are not bifurcated. Caudal vertebrae are relatively short and thick. The anterior caudal vertebrae are slightly amphicoelous. The chevron of the 1st caudal vertebrae is connected with the 1st caudal and is shallow and small. Whereas the 1st caudal vertebrae of Omeisaurus tianfuensis have no chevron. The rib of the 1st caudal vertebrae are laterally directed, while the first caudal rib of the other species of Omeisaurusare prominently enlarged distally, being slightly fan-shaped. Humerus is long and straight, with slightly expanded proximal end and greatly expanded distal end. The deltopectoral crest is well-developed and relatively low. Femur has a slender shape, with a greatly expanded proximal and distal ends. The fourth trochanter is well-developed. The ratio of the humerus length to femur length is approximately 0.83, the ratio of the ulna length to humerus length is approximately 0.72, the ratio of the tibia length to femur length is approximately 0.63.