Cave 8 is the largest of the caves at Tianlongshan with the exception of Cave 9, the colossal Buddha cave. It is the only central pillar cave at the site and the only cave known to be of the Sui dynasty (581-618). It has a porch three bays wide that is largely preserved. The traces of two guardian figures standing at the sides of the entrance can still be seen. At the right side of the porch there is a stele with a long inscription dated to the fourth year of the kaihuang reign period, or 584. It records the persecution of Buddhism in the preceding Northern Zhou period after the conquest of Northern Qi, and its restoration with the rise of the Sui dynasty. The cave is dedicated by a Sui official to the well-being of the Sui emperor Wen (r. 581-604) and his son Yang Guang, the prince of Jin.
The main chamber of Cave 8 is square in plan with a large square central pillar. It has three niches around the back and side walls and four niches on the central pillar, each with a central seated Buddha and standing attendants.