The first fossils of Saichania were found in the early 1970s in Mongolia. In 1977 the type species Saichania chulsanensis was named. The description of this species has been based on limited fossil material; especially the rear of the animal is not well known.
Saichania was a large ankylosaurid. Maryańska estimated its length at seven meters. Other estimates roughly confirmed this, stating a maximum length of about 6.6 metres (22 ft) long. However, Gregory S. Paul in 2010 gave a lower estimate of 5.2 metres, with a weight of two tonnes. Finds of tail clubs of gigantic individuals suggest larger sizes but their reference to Saichania cannot be substantiated as the holotype, the only specimen sufficiently described, only consists of the front of the animal.
Saichania shared the general ankylosaurid build, being a low-slung, broad, heavily armoured dinosaur, with short forelimbs. Even for an ankylosaurid however, Saichania is exceptionally robust, its rump strengthened by ossifications and fusions of the vertebral column, ribs, shoulder girdle and breast bones.
Saichania was over five metres long and weighed over two tonnes. It was more robustly built than other members of the Ankylosauridae. Neck vertebrae, shoulder girdle, ribs and breast bones were fused or firmly connected. Its body was flat and low-slung, standing on four short legs. The forelimbs were very powerful. The head was protected by bulbous armour tiles. It could defend itself against predators like Tarbosaurus with a tail-club. On the torso keeled osteoderms were present. Saichania bit off plants in its desert habitat with a horny beak and processed them in its wide hindgut.
It is belived that Saichania lived in a hot, arid, desert-type environment – and it seems to have possessed a number of adaptations to this environment. Saichania’s skull was equipped with complex air passages that would have helped it keep cool. Additionally, it may have a salt gland near its nostrils.
The holotype preserves the front body armour in articulation. The neck is protected by two cervical halfrings, each made of six rectangular segments positioned next to each other: two at the top, two at the upper sides and two at the lower sides. Each segment has a keel parallel to the long axis of the body. The keel of the lower side segments is the largest. The segments are connected to an underlying continuous band of bone, mainly by a broad fusion at the front edge, but also by a narrow strip at the rear. The seams between the segments are covered by a rectangular zone of small oval osteoderms. Between the upper and lower side segment a larger central osteoderm is present, forming a rosette. The front halfring is smaller than the rear one.
Maryańska classified Saichania as a member of the Ankylosauridae, related to Pinacosaurus and observed that these two dinosaurs differ from all others in the structure of their nasal cavities.