Abstract: Oil and gas exploration and production from the marine carbonate reservoirs have entered a blooming period in theTarim Basin. Due to lack of enough drilling core data, the study of palaeokarst reservoirs is faced with difficulties. As an alternative, the only way is to carry out the studies on the Ordovician weathering crust and the karst cave system and their evolution through outcrops, which are well developed in the Tabei area. Our research shows that the development of palaeokarst is mainly controlled by lithology and the unconformities, mainly in the Yijianfang Formation. The main karstification period is in conjunction with the time when the hiatus between the Tumuxiuke group and the Yijianfang group was formed. The results are significant for understanding and modeling of the underground cave system.