Abstract: Northern Jiangsu Depression is a fault-down basin of 32,000 km² located in the second uplifted belt of NNE trending-Neocathaysian tectonic system. Sediments have been deposited since Paleozoic, of which the Tertiary is especially important for oil. This paper consists of three parts. l.The sporo-pollen and ostracoda assemblages in Taizhou Formation of the early, middle Paleocene and its time attribution are outlined. 2.In the light of the features of sporo-pollen and ostracoda. assemblages, the palaeoclimate, palaeovegetation and palaeogeography environments of deposition period of Taizhou Formation are discussed. 3.By using the distribution, taphonomy, differentiation, evolution and type characteristics of sporo-pollen and ostracoda fossils, the relationship between the environment of deposition period of Taizhou Formation and the source rock sequences are expounded.