In order to analyze the impact of rectification of water conveyance structures on the water diversion capacity of the Middle Route Project of the South-to-North Water Diversion Project, taking the section from the gate of Taocha canal to the Shierlihe aqueduct as an example, a coupled one- and two-dimensional hydrodynamic model was established, with the one-dimensional model adopted for the channel section and the two-dimensional model adopted for the sections of the four water conveyance structures (the Diaohe aqueduct, Tuanhe aqueduct, Yanlinghe aqueduct and Qihe inverted siphon). The coupled model was calibrated with multi-year measured data. Fifteen rectification schemes and a scheme without rectification were simulated to analyze the impact of different schemes on the upstream and downstream sections and to explore the rectification scheme with the minimum head loss. The results show that the impact range of rectification is from 3 to 5 km upstream and downstream of a single structure and the cumulative effect of multiple structures is less than that of the linear superposition of single structures. The effect of rectification of the two water conveyance structures (the Tuanhe aqueduct and Yanlinghe aqueduct) in the middle of the channel section is better than that of the two water conveyance structures (the Diaohe aqueduct and Qihe inverted siphon) in the upstream and downstream sections.