Silicalites are widely distributed in the Middle Permian Maokou Formation in eastern Sichuan basin. Based on detailed observation in the field and the contents of major elements, REE and isotope of silicalites, it is suggested that the Maokou Formation silicalites were hydrothermal origin and were deposited on inter-platform basin environments. The contents of SiO2 are relatively high, and the value is 80.09%~97.91%. The ratio of Al/(Al+Fe+Mn) is regarded as a helpful criterion for identifying hydrothermal silicalites from other silicalites. The average ratio is 0.30 in the Maokou Formation. The REE contents of silicalites are low (7.509×10-6), with mid enrichment of HREE and negative anomaly of Ce. The values of δCe vary from 0.391~0.812. The values of δEu are maily 0.736~6.106, which are normal or slightly positive abnomal values. The Silicon (δ30Si) and Oxygen (δ18O) isotope compositions are correlated with the hydrothermally sourced quartzs. The paleotemperatures of the sea water, inferred from the Oxygen isotope records, is 34.45~88.92℃ during the formation of the silicalites. There were many syndepositional faults and volcanisms of Permian in eastern Sichuan basin. In addition, the heat source responsible for the hydrothermal convection is also presented in study area. Studied section is close to the Qiyaoshan fault, which could be the pass of hot liquid from deep crust. At that time, sea water encountered and was heated with magmatic liquid, and then dissolved much SiO2 and other elements. The warmer sea water with dissolved SiO2 sprayed out from the faults, which resulted in the enrichment of SiO2 in the sea waters and the consequent silicalite deposition in adjacent areas.