To enhance the adaptability of hydrological model structures to the spatiotemporal heterogeneous characteristics of catchment runoff generation and routing and improve the applicability limitations of traditional fixed-structure models in different catchments, the fundamental principles of the SuperflexPy modeling framework based on the flexible architecture theory were systematically elaborated. By taking the Qijiang River Basin in Chongqing as the study area, a semi-distributed catchment hydrological model was constructed. A comparative test was carried out through 18 assembly schemes of hydrological process elements, and the daily runoff simulation effects of different model structures were quantitatively evaluated. The results indicate that the semi-distributed hydrological model constructed based on SuperflexPy can effectively simulate the daily runoff processes at catchment control sections; the simulation results of different element assembly schemes show significant differences, which can effectively identify and reflect the key hydrological links in the runoff formation process; SuperflexPy adopts an object-oriented paradigm to achieve the modular encapsulation of hydrological elements and generalizes the catchment topological structure through the hierarchical organization of simulation units, nodes, and networks. It can flexibly assemble different runoff generation and routing processes, possesses strong catchment adaptability, and can well depict the spatiotemporal heterogeneity of catchment runoff generation and routing.