The bedded cherts which are in conformity with the stratum of the first Member of Doushantuo Formation and chemical precipitation originally, are discovered in the “Cap Carbonates” of Three Gorges region of Hubei Province. High compositions of δ30SiNBS-28 (0.4~1.7‰) of the bedded cherts indicate that the environment of silicate precipitate are littoral facies; for the δ18OV-SMOW value of the bedded cherts are 24.0~26.6‰, geothermometers of quartz-seawater oxygen isotope fractionation estimate that the temperature of chert sedimentary is 49.7~64.5℃. In consideration of metamorphism during the later stages, estimated the seawater temperature is 49.7℃. The ratios of Al/(Fe+Mn+Al) and Si/Al are respectively 0.43~0.50 and 257~269, indicate a few terrigenous matters mixed in the progress of silicate sedimentation, while the values of ∑REE and U/Th indicate a Hydrothermal Sedimentary Genesis. Therefore, the origin of silicate maybe supplied from a distal volcanic hydrothermal activity and precipitated as bedded cherts in warm littoral facies when the concentration of silicate basic saturated，and this work verificated a guess proposed from early researchers that the evironmental temperature for cap carbonates was once hit to 50℃.