Abstract: Mammalian fossils were collected from Baiyundong Cave (White Cloud Cave, 34 0 17' N, 117 0 18' E), Xuzhou, Jiangsu Province. The mammalian fauna in Baiyundong Cave is similar to that of Loc. I at Zhoukoudian. The mammal fossils found from the cave contain 9 species belonging to 9 genera, 7 families, 4 orders, as listed in Chinese text. Most of the species were also found at Loc. I of Tangshan (Xu et al., 1993; Mu et al., 1993). There are two mammalian faunas in Middle Pleistocene. One is the Chenjiawo fauna, and the other is the Peking Man fauna or the Zhoukoudian fauna. The Chenjiawo fauna is the temperate Quaternary fauna of the archaic type. Its geological period is correlated with Stages 14—29, ranging from 500 000 to 1 000 000 years ago. While the Peldng Man fauna is the temperate Quatemary fauna of the evolved type. Its geological period corresponds to Stages 6—13, ranging from 127 000 to 500 000 years ago (Table l). Cricetinus varians LSD is correlated with Event 9 in America and Europe and marks the first appearance of the Peking Man fauna in Zhoukoudian (Repenning, 1987; Xu, 1996). So the geological age of the faunas at both Baiyundong Cave and Loc. I at Tangshan corresponds to that of the Peking Man fauna.