Objectives: Quantitative analysis of submarine canyon confluence processes in salt diapir-affected regions is critical for understanding deep-water sedimentary systems, yet the three-dimensional hydrodynamic mechanisms and morphodynamic interactions under structural controls remain poorly understood. This study investigates the Dorsey-Sounder Canyon System in the northern Gulf of Mexico to systematically reveal the salt diapir-driven three-dimensional morpho-hydrodynamic evolution, sediment partitioning patterns, and associated depositional mechanisms. Methods: Integrated analyses of high-resolution 3D seismic data, automated canyon morphology identification, and hydrodynamic quantitative modeling were combined to reconstruct the spatiotemporal evolution of the canyon confluence zone. Multidisciplinary approaches focused on: (1) quantifying morphological parameters, (2) analyzing flow pathway dynamics through hydraulic modeling, and (3) deciphering erosional-depositional patterns under salt tectonic constraints. Results: The modern trunk canyon comprises an eastern tributary and a post-confluence segment, with the confluence point migrating ~1 km southeastward from the initial scour zone, forming a trumpet-shaped morphology characterized by pronounced widening and deepening. Salt diapirs dominantly controlled the confluence process through three-dimensional mechanisms: (1) Planar structural steering confined canyon pathways and defined the confluence zone; (2) Enhanced vertical confinement promoted incision and erosional amplification; and (3) Differential diapir growth rates governed confluence migration. These processes drove asymmetric sediment partitioning and distinct architectural stacking in the deep-water system. Conclusions: This work establishes the first integrated 3D model of salt diapir-controlled canyon confluence processes, elucidating how salt tectonics regulates sediment routing and reservoir heterogeneity in deep-water settings. The findings provide a predictive framework for analogous salt-affected basins, emphasizing the coupling between structural evolution and sedimentary responses in source-to-sink systems. This advances theoretical foundations for hydrocarbon reservoir prediction in complex deep-water environments.