Yongjinglong was first described and named by Li-Guo Li, Da-Qing Li, Hai-Lu You and Peter Dodson in 2014 and the type species is Yongjinglong datangi. The generic name is derived from the name of the historical Yongjing County, near where the holotype of Yongjinglong and numerous dinosaur track fossils were collected, and from long, meaning "dragon" in Chinese. The specific name, datangi, honors the Tang dynasty and also Mr. Zhi-Lu Tang from the IVPP, for his contributions to the study of dinosaurs.[1]
Yongjinglong was a medium-sized sauropod. The describers established some diagnostic traits. The premaxillary teeth are long and spoon-shaped. The neck vertebrae and anterior dorsal vertebrae possess large and deep pleurocoels, pneumatic depressions, that cover the entire sides of the centra. The ridges on the sides of the middle dorsal vertebrae form a pattern shaped like a "XI", with the "X" in front. The spine of at least one middle dorsal vertebra is low and not bifurcated and forms with the postzygapophyses a triangular bone plate, directed upwards. The shoulder blade is extremely long, with, in side view, exceptionally straight front and rear edges.[1]