Quartz sandstone, namely the “Luotuobo Sandstone” dominated the lowermiddle parts of the lower submember of Member 8 of the Middle Permian Xiashihezi Formation in the Wushenqi Gasfield in the Ordos Basin, while its upper part is characterized by dark color silty mudstone or carbonaceous mudstone. The “Luotuobo Sandstone” is widely distributed in the North China Platform, is developed in the whole Ordos Basin, and is one of the main reservoirs of the basin. Previous researchers considered that the lower submember consists of fluvial or delta facies. By core observations on the lower submember in many wells, it is proved that the lowermiddle part of the lower submember consists of beach and bar facies, while the upper part is marsh facies or is dominated by marsh facies intercalated with channel deposits. The composition and texture maturity of the quartz sandstones in the lower submember is high. One sandstone interval or two sandstone intervals were developed in the lower submember. The two sandstone intervals were intercalated with severalmeters dark color silty mudstones of semideep lacustrine facies or carbonaceous mudstones of marsh facies.  Sedimentary structures such as flush crossbedding with angle lower than 10°， hummocy crossbedding were developed. The GR curves are box type or toothlike box type. Many thickbedded sandstones make up eastwest oriented lanticular sandbodies and they approximately parallel to the paleoshoreline.