The fossil remains of Hudiesaurus were in 1993 found by a Chinese-Japanese expedition near Qiketia in Shanshan, Xinjiang province. The type (and only named) species, Hudiesaurus sinojapanorum, was named and described by Dong Zhiming in 1997. The generic name is derived from Mandarin hudie, "butterfly" and refers to a flat butterfly-shaped process on the front base of the vertebral spine. The specific name refers to the members of the expedition but can also be read as "central part" in Chinese, a pun on the Japanese Chunichi Shinbun (again "central part") press group, which financed the research.
Hudiesaurus is known from only two incomplete specimens, uncovered in the Kalazha Formation of the Turpan Bassin, which perhaps dates to the late Jurassic Period. The type specimen (IVPP V 11120) is represented only by a very large anterior dorsal vertebra. Another partial skeleton from an apparently smaller individual found about a kilometre away from the holotype, consisting of a nearly complete right front leg and teeth, specimen IVPP P. 11121, has by Dong been referred to this species. Paul Upchurch in 2004 rejected the identity because of a lack of overlapping material.
Although the specimens are fragmentary, Hudiesaurus is believed to have been very large, even for sauropods, given the considerable length of the vertebral centrum of fifty-five centimetres. Dong estimated a body length of about thirty metres (hundred feet).
Dong thought Hudiesaurus may have been related to Mamenchisaurus and accordingly placed it in the Mamenchisauridae. Upchurch in 2004 limited the precision to a more general Eusauropoda.