Abstract: Through the statistics, analysis and correlation of large amounts of microfossil plants found in the Tangjiawu Formation, the author has established the Moyeria cabotti-Leiospharidium wenlockia assemblage zone of the Tangjiawu Formation. This assemblage zone contains 14 genera and 22 species. The age of the Tangjiawu Formation is assigned to Middle Silurain （Wenlockian）. The large amount of microfossil plants found in the Xihu Formation include 30 genera and 70 species. Through study and correlation the author suggerts that the age of the Xihu Formation is late Late Devonian （Famennian）.