Abstract: The sandstone of Huangliu formation in Dongfang area of Yinggehai basin is characterized by obvious high?temperature and overpressure diagenetic environment. By means of thin section, cathodeluminescence, SEM, enclosure, X?ray, etc, this paper studied the diagenetic characteristic of Huangliu sand under high?temperature and overpressure and its effect on the reservoir quality. This sandstone with poor compaction and strong corrosion has crystallized with such authigenic minerals of hydrothermal origin as siderite, barite and rutile, etc. Under the high?temperature and overpressure, the primary porosity was not only preserved mostly, but also favorable to forming a great amount of secondary pores for dissolution of the high temperature hydrothermal fluid on feldspathic mineral. The cementing of siderite, ferrocalcite and ferrodolomite and the filling of authigenic kaolinite were resulted in lower porosity of the reservoir, while the rapid smectite?illite conversion could be the main reason for quick decline of the reservoir permeability. The studied result shows that the hightemperature and overpressure could not only preserve the primary porosity in this reservoir, but also result in a great amount of corrosion of unstable minerals. Conducting research of the reservoir development mechanism under high?temperature and overpressure is of great significance for prediction of“dessert”in the sandstone reservoir