Abstract: The Xinchang Basin in eastern Zhejiang Province contains a series of diatomite deposits interlaid in the basalts of the Miocene Shengxian Formation. The geochemical characteristics of deposits can provide crucial constraints on the Miocene palaeoenvironment of the eastern Zhejiang Province. In this study, three typical diatomites from the Fuquanshan volcano in Shengzhou City have been analyzed. Compared to the typical diatomites worldwide, low SiO₂ (61.3％~69.4％), high Al₂O₃(14.6％~17.9％), and REE contents indicate that the Fuquanshan diatomites contain high proportions of fine detritus. Compared with the associated basalt of Shengxian Formation, the composition of the diatom is obviously enriched in large ion lithophile elements and light rare earth elements, with negative anomalies of Eu, Nb and Ti, similar to those in Cretaceous acid volcanic. Based on REE and incompatible elements characteristics, the fine detritus of the Fuquanshan diatomites were mainly derived from the Cretaceous silicic volcanic rocks, rather than coexisting basalt. Chemical weathering index, Sr/Ba ratio, etc., combined with previous paleontological studies support that the Miocene Fuquanshan diatomite deposits were formed in the freshwater lake under a warm humid climate, which is distinct from the Paleogene drought climate of eastern Zhejiang. Miocene diatom "Boom" in eastern China reflects the regional tectonic and palaeoenvironment transformation in the turn of Paleogene-Neogene.