In order to figure out the influence of SiO2 to reservoirs property, such as physical property and brittleness, in the shale system of middle Permian series Lucaogou Formation in Malang sag, Santanghu Basin in Xinjiang, SiO2 occurrence and origins of different occurrences for samples from the Lucaogou Formation was studied by a series method, including XRD of whole rock and clay minerals, mechanical properties of rocks, cathode luminescence, SEM and EDS, then on the basis of these analysis, the effect of the content of quartz on reservoir property was explored. The research indicates that silica in tuff, mud shale and silty mudstone is mainly amorphous and displays irregularly in tuff, while can be any geometry in others. However, silica in tuffaceous mudstone and tuffaceous dolomite shows crystal morphology. Silica in tuffaceous mudstone shows as authigenic quartz gathering like ribbon, and occurs separately in tuffaceous dolomite, while silica in dolomite is in the stage of Opal A/Opal CT. Tuffaceous matter and its devitrification provide silica and space for authigenic quartz formation. They are the key factors of SiO2 occurrence. Furthermore, porosity, permeability and compressive strength have a positive relationship with the content of quartz, while Poisson’s ratio has a negative relationship with quartz.