Found in the Lower Shaximiao Formation, Huayangosaurus shared the local Middle Jurassic landscape with the sauropods Shunosaurus, Datousaurus, Omeisaurus and Protognathosaurus, the ornithopod Xiaosaurus and the carnivorous Gasosaurus.

Like its more famous relative, Stegosaurus, Huayangosaurus bore the distinctive double row of plates that characterize all the stegosaurians.

On the rear of the tail, pairs of spikes were present forming the so-called "thagomizer", a defensive weapon.

Each flank had a row of smaller osteoderms, culminating in a long shoulder spine in front, curving to the rear.

[2] Huayangosaurus was one of the smallest known stegosaurians, at just 4 metres (13 ft) in length and 500 kilograms (1,100 lb) in body mass.

[3] In 1979 and 1980, remains from twelve stegosaurian individual animals were recovered from the Dashanpu Quarry near Zigong in Sichuan.

Two large spikes were above its hips, and may have been used for deterring an attack from above (considering as it was fairly short in height compared to later stegosaurians).