In early Hercynian period, epigenic karst, semi open confined karst, and buried confined karst are developed in the Middle-Lower Ordovician of Tahe Oilfield, Tarim Basin, of which the semi open confined karst is developed in the shallow coverage zone. There are giant oil and gas resources in karst fracture-cave reservoirs of Middle-Lower Ordovician in the shallow coverage area of Tahe Oilfield. Confined by the Upper Ordovician Lianglitage Formation and deep insoluble beds, the fracture-cave reservoirs of Middle-Lower Ordovician in the shallow coverage area show typical strata-bound distribution characteristics. Karst conditions and karst fracture-cave structure in shallow coverage area are different from those of exposed karst controlled by drainage base level and buried karst with deep-circulating. In order to clarify the karst genetic mechanism and fracture-cave structure of Middle-Lower Ordovician of T738 well block in the Upper Ordovician shallow coverage zone of Tahe Oilfield, the residual thickness trend combination method which takes advantage of both the residual thickness method and the construction trend surface method, was used to restore the ancient landform and ancient water system of the Early Hercynian, and the insoluble beds and cave beds were identified by logging and seismic methods. Furtherly, combined with the dynamic production characteristics of the reservoir, the transverse-rising fracture-cave structure model under the confined karst conditions in shallow coverage area is constructed. The results show that: (1) The Early Hercynian paleogeomorphology is generally high in the northeast and low in the southwest, with shallow-cutting dendritic surface water system developed in NE-SW direction, and the northern exposed area provides high hydraulic gradient and high-flow karst water supply. (2) T738 well block is in semi open confined karst conditions, and three sets of insoluble beds (the Chalbach Formation-Lianglitage Formation, the bottom dense section of the Yijianfang Formation, the lower section of the Yingshan Formation) and two sets of cave maze beds (the Yijianfang Formation and the upper section of the Yingshan Formation) are developed in Middle-Lower Ordovician. (3) Influenced by factors such as insoluble beds, hydrodynamic gradients and faults, the cave beds in Yijianfang Formation and the upper section of Yingshan Formation have longitudinal hydrodynamic relations, and four types of confined karst fracture-cave structures, including transverse-rising type, isolated type, transverse type and blind end type, are developed. The research results have important geological guiding significance for the development of fracture-cave reservoirs of T738 well block in shallow coverage zone of Tahe Oilfield.