The Honghuagou area of Chifeng City is tectonically located on the northern margin of the Inner Mongolian axis. Microfossils were collected from siliceous marble at East Hill of Shitoudao Village, in the western part of the Honghuagou gold mine. Fossils described here include 12 groups, 20 genera (2 new) and 20 species (3 new, 1 cf. sp. and 10 sp. indet. ), such as Hy- olithids, Hyolithelmithes, Shiphogonuchitiida, Conodomorpha, Chanceloriida, Protoconodonta, Globomorpha, Monoplacophora, Operculum, Worm-tubes, and Algae. There are many mem-bers of the Meishucun fauna always developed in southern China and also elements of the Qinghezhen fauna. Among the above taxa, Protoclosterium lenis Tan (gen. et sp. nov. ) may be divided into three types of joining according to the characteristics of the apical end: (1) joining in the same direction; (2) dislocated joining in the same direction; and (3) joining in different di-rections. The siliceous marble bearing the microfossils which was originally assigned to the Archean may be considered to be of Late Sinian-Early Cambrian age.