The Popei have been officially combined with dozens of other distinct ethnolinguistic peoples to form the Yi nationality in China. The Popei are widely known by their Chinese name, Shui Yi, meaning "water Yi." The Popei (Shui Yi) are often mistaken for the Shuitian (Watery Fields) group, but the two groups are distinct and speak separate languages. Popei is this group's autonym.

Today's various branches of the Yi people, including the Popei, are believed to have come from common stock. Legends and records written in the ancient Yi script show that the Yi society was once matriarchal. The Annals of the Yis in the Southwest records that in ancient times the Yi people "only knew mothers and not fathers ... and women ruled for six generations in a row." As the Yi splintered into numerous divisions and migrated throughout southern China, each group gradually developed its own language and culture.

Although small in number, the Popei celebrate many traditional Yi festivals. Some of these include the Garment Contest Festival which takes place in Zhijie Township of Yongren County every February; and the Get-Together of Princes Festival which is held in Longjie Township of Dayao County on the eighth day of the fourth lunar month. The people throw water over each other, sing, dance, and create an edible "prince" which they bake and eat.

As the Popei were gradually absorbed by the Han Chinese, they adopted many of the Han's Daoist and ancestor worship rituals.

The region inhabited by the Popei is one of the least evangelized in all of Yunnan Province. Various hidden tribes and groups in the area are locked away by remote mountains and rushing streams. Roads into the area were only constructed in the 1950s. Before then access was only possible by foot or on horseback from the nearest town. The nearest churches are among the Nasu and Lipo in Wuding.