Abstract: In previous studies on volcanic rock of Woniusi Formation in Shidian region, some researchers have proposed it has close relation with the marine volcanic activity as in Baoshan region, north Yunnan Province. However, the inexistence of sediment strata and characteristics of petrology, geochemistry and geology indicate that the eruption environment is significantly different between the two regions. It is showed that the Woniusi Formation form in continental eruption setting and associated with the continental flood magma in Shidian region. In addition, the age (264 Ma) of volcanic rock from Woniusi Formation and the contact relationship with upper and lower strata suggest the Woniusi Formation might be formed in Early Permian, and these provide new evidence for the formation age of Woniusi Formation.