Pores are widely developed in the dolomite of the Lower Ordovician Penglaiba Formation-Yingshan Formation in the Gucheng area,Tarim Basin,which are characterized by needle-like dissolution pores,ultra-grain pores,intercrystalline micropores,etc.,and are generally considered to be related to dolomitization.Based on data of core,thin section,cathodoluminescence,inclusions,rare earth elements,carbon and oxygen isotopes,etc.,the genesis,pore types and genesis,pore evolution model of dolomite in the Lower Ordovician Penglaiba Formation-Yingshan Formation in Gucheng area are analyzed.The results show that:(1)The dolomite is dominated by penecontemporaneous dolomitization,partially superimposed by deep thermal fluid,and the dolomite filling in the fracture-vug is of hydrothermal origin.(2)The super-grain pores are macroscopically needle-like dissolution pores,which are developed in fine-medium crystalline dolomite with original fabric as particles,mainly being medium-big pores,and are mostly developed in the middle and upper parts of a single grain shoals cycle.They are intragranular dissolution pores,mold pores and intergranular dissolution pores formed by selective dissolution of atmospheric fresh water in the penecontemporaneous period before dolomitization.The intercrystalline micropores are isolated with poor connectivity and are formed by penecontemporaneous dolomitization.Although the penecontemporaneous dolomitization did not directly produce a large number of pores,it provided a framework that resisted compaction and hindered the later fluid precipitation,which was the key to the preservation of pores.(3)The porous-type dolomite reservoir of Penglaiba Formation-the lower member of Yingshan Formation in Gucheng area of Tarim Basin is characterized by multiple sets of thin layers.Its thickness and scale are affected by the superposition of multi-stage granular shoals and their exposure degree.Exploration for this type of reservoir should be focus on the high areas of paleogeomorphology where are conducive places to the development of dolomitization granular shoals.