The surface features of quartz grains can be used as an indicator for their depositional environments due to its large hardness and high chemical stability. And Scanning Electron Microscopy is a useful tool to identify the features of quartz grains. The Cretaceous in the Simao Basin was generally considered to be hydrothermal deposit, however, after field identification and indoor basic research, the authors consider that the Mangang Formation in the Jinggu area shows typical features of eolian sediments, so much research on surface features of quartz grains is needed to figure out the sedimentary facies. The result shows that quartz grains of the sample of the Mangang Formation in the Jinggu area are well rounded, and massively developed dish shaped impact scars, crescent shaped impact scars, and frosted surface, thus suggesting typical features of eolian environment. The surface features are different from those in aqueous environment. The high intensity dissolution and precipitation indicate the dry and hot climate. Based on the fact that they are in origin eolian deposits analysis of the Mangang Formation in the Jinggu area, sedimentary features such as typical sedimentary structure, grain size analysis, lithologic features, etc, authors finally considered that it belongs to desert deposit.