Two sets of siliceous shale formations in Lower Paleozoic are the important shale reservoirs in Sichuan Basin,and the TOC and shale gas content are positively related to the siliceous quantity,suggesting that the siliceous materials could be very important for the shale gas formation.However,the origin of siliceous materials is complicated,and there could be some siliceous fluid filled after the rock sedimentation.This study,based on the summary of previous research results, has carefully analyzed the petrographical characteristics of siliceous minerals.Three types of siliceous sources have been detected:①syngenetic hydrothermal inorganic siliceous fluid,②bio-silica,and ③late-filled inorganic siliceous fluid.Syngenetic hydrothermal inorganic siliceous fluid and bio-silica are the dominated siliceous sources in Lower Cambrian shales.Syngenetic hydrothermal inorganic siliceous fluid made the organic matter rapidly silicified,and the organic matter could be exquisitely preserved.The siliceous source in the Wufeng—Longmaxi Formation was mainly from late-filled inorganic siliceous fluid and bio-silica,and organic matter preservation has little influence by siliceous fluid.Thus,the organic matter has gone through slowly saprofication process,resulting in the morphology of organic matters are poor preserved.The study has initially revealed the petrographical characteristics of siliceous materials and the influences on the organism preservations for comparision the Lower Cambrian and the Wufeng-Longmaxi shale reservoirs,with hoping to provide new geological data and ideas for shale gas exploration in Sichuan Basin.