The Xihu depression in the East China Sea basin contains significant oil and gas resources. The Pinghu Formation coal measures are the primary source rock and oilgas reservoirs. In order to better understand its tectonic setting, provenance characteristics and paleoenvironment, we conduct detailed geochemistry study of the argillaceous rocks of the Eocene Pinghu Formation. LaThSc and ThScZr/10 diagrams indicate that the study area was mainly subjected to the continental island arc and active continental margin tectonic background. Argillaceous rocks were predominantly derived from upper crustal felsic igneous rocks based on the values Al2O3/TiO2, K2O/Al2O3, Cr/Zr, LREE/HREE, Eu, LaN/YbN, GdN/YbN and plots of Th/UTh, and the fairly uniform REE patterns. By comparing the characteristics of the magmatic rocks in the uplift area, it is concluded that the parent rocks are mainly granitic amphibolite and ingenious tuff, with a few andesites and metamorphic rocks. The ACNK triangle showed that mudstones were affected by the K metasomatic processes, and in this regard, we corrected the chemical index of alteration (CIA). The Eocene Pinghu Formation mudstones have moderate to high Kcorrected CIA (6140~8349), indicating moderate to intense chemical weathering conditions. By analyzing and comparing with the CIA of the Oligocene Huagang Formation, the chemical weathering history suggests that a warm and humid climate during the Eocene, whereas a cool and humid to semihumid climate prevailed during the Oligocene. Using the corrected boron contents (Bc) and integrating the analysis of paleomorphological and paleontological features, it is concluded that there is regional variability in the depositional background of the Pinghu Formation. The northern part (A1) shows a terrestrial depositional environment as a riverdominated deltaic depositional system. The central part (A2) and southern part (B1) were dominated by the marginal marine environments as the tidally influenced deltaic depositional system. Trace element U/Th ratios, V/CrNi/Co and MoNi/Co discrimination diagrams indicate that the mudstones of the Pinghu Formation were formed in an oxic environment.