The Ordovician composite-genetic karst carbonate reservoir in No. 12 block of Tahe oil field is rich in oil and gas reserves. Yet the formation of the reservoir is controlled by multiple kinds of paleo-karst mechanism, which brings to a big challenge for characterization of its complex architecture. Based on diversified research data of multiple scales, the architecture system of the reservoir is established, and a geomodeling scheme of “structural constraining, hierarchical modeling, and classifying-merging” is proposed. The results show that based on a combined principle of genesis, scale, and configuration, the reservoir in the composite karst area is divided into three architecture systems: paleo-underground river, fault-controlled system, and unconformity-controlled system. Paleo-underground river hierarchy has two levels: (1) by constraint of structure segmentation points, the envelope model of the underground rivers is established with deterministic method based on acoustics impedance truncation; (2) by constraint of envelope and GR-nonlinear-inversion attributes, the internal filling model of the underground rivers is established by sequential gussian simulation (SIS). The fault-controlled system hierarchy has two levels: (1) the fault controlled vug envelope, and (2) the faults and fault-controlled caves. Bsaed on curvature-ant as well as impedance attributes and drilling calibration, the geomodels of class-II and class-III order faults and fault-controlled caves are established with deterministic method through attribute cut-off. Using drilling data, under constraint of geological and seismic probability model, the fault-controlled pore-vug model is established by SIS method. Finally, a typical fault-karst reservoir in S94CH area, Tahe oilfield, is studied as an example to test the modeling method mentioned above, and static connectivity of the model is coincide with the dynamic data in the well district.