Hydrostratigraphic frameworks are essential for understanding karst groundwater flow and the formation mechanisms of pore and cave reservoirs. The southern Tahe area is covered by Upper Ordovician strata and is characterized by a semi-confined to confined karst hydrogeological setting. Therefore, the establishment of a hydrostratigraphic framework is particularly important under these conditions.Three-dimensional seismic data, conventional well-log data, and core observations were used in this study. Porosity was calculated from well-log parameters. Lithology and types of porous media were integrated. Aquifers and aquitards in individual wells were classified according to fluid-flow characteristics. A multi-well hydrostratigraphic correlation framework was then established. The spatial distribution of the hydrostratigraphic units in the southern Tahe area was characterized.Four types of Ordovician hydrostratigraphic units were identified in the Tahe area. Intervals with matrix porosity greater than 2% are defined as diffuse-flow layers. Intervals with well-developed dissolution vugs and fracture-related vugs are defined as vug-dominated flow layers. Fracture-dominated intervals are defined as leaky low-permeability layers. Fully compacted intervals are defined as tight low-permeability layers. The first-order hydrostratigraphic framework consists of four units. The lower aquifer is represented by the dolostones of the Penglaiba Formation. The cave-bearing layer extends from the lower Yingshan Formation to the lower sub-member of the upper Yingshan Formation. The upper aquifer extends from the upper sub-member of the upper Yingshan Formation to the Yijianfang Formation. The overlying confining layer is formed by the Upper Ordovician strata. In the second-order hydrostratigraphic framework, the upper aquifer is subdivided into two secondary aquifers separated by one secondary aquitard. One secondary aquifer is identified between two secondary aquitards within the cave-bearing layer.The vertical differentiation of the hydrostratigraphic framework is mainly controlled by the lithostratigraphic succession. Favorable reservoir properties are controlled by high-energy lithofacies. The distribution of aquifers is controlled by intervals with favorable reservoir properties. The established hydrostratigraphic framework reveals that the Ordovician strata in the southern Tahe area possess geological conditions favorable for stratified karst groundwater flow. It also provides an important basis for understanding the formation mechanisms of middle-to deep-level karst caves in this area.