The black shale in the lower part of the Wufeng and Longmaxi Formations in the Western Hubei Province has become a hot spot for shale gas exploration in South China. In this paper we investigate the origin and source of siliceous minerals in the black shale from both these formations by systematic collection and analytical testing of samples, and examine the impact of different original silicon on organic matter accumulation and reservoir characteristics. The results show that the black shale of the Wufeng and Longmaxi Formations in the study area has a high content of siliceous minerals. The excess silicon content ranges from 2. 59%~88. 31% (average of 27. 91%) and most excess silicon develops in the deepshelf environment corresponding to the Katian and Rhuddanian Stages. Angular terrigenous quartz and siliceous fossil such as radiolarians and sponge spicules with serrated edges can be observed under the microscope. Element geochemistry analysis indicates that the average content of TiO2 and Al2O3 in samples is only 0. 63% and 12. 41% respectively, and the relationships between SiO2 and TiO2, Al2O3 are negative. The ratio of Si/(Si+Al+Fe) and Al/(Al+Fe+Mn) is 0. 81 and 0. 77, and Eu/Eu* has a clear negative anomaly. Excess silicon does not have linear relationship with U/Th and Ni content. The above data demonstrate that the terrigenous silicon and biosilicon are the main sources of siliceous minerals in the black shale of the Wufeng and Longmaxi Formations, and hydrothermal silicon has little impact on the origin of siliceous minerals. Deepwateranoxic and reducing environment should provide favorable conditions for the development of biosilicon, but the biosilicon has no clear linear relationship with paleoproductivity and redox conditions as demonstrated by the normal distribution curve relationship between the high value of TOC and the contents of different original silicon. The normal distribution curves show that when the content of Al2O3 and excess silicon are around 10% and 40% respectively, the TOC of shale will have highest value, which indicates the complicated relationship between organic matter accumulation and siliceous mineral content. Furthermore, the development of siliceous mineral, especially the biosilicon with microcrystal occurrence can not only provide effective protection for reservoir space, but also promote the development of microfractures, which can greatly improve the reservoir capacity and flowing ability, as well as the reservoir fracturing reformation effect.