This paper reviews the research progress on the unique hydrodynamic and mixing characteristics in open channel confluence areas, focusing on the complex flow structures influenced by factors such as convergence ratio, intersection angle, bed elevation difference, and other parameters. Key features such as separation zones, shear layers, and secondary circulations are discussed. The paper integrates findings from physical model experiments, numerical simulations, and field observations, summarizing the current state of research on hydrodynamics and mixing characteristics. Based on existing challenges, future research should focus on the application of artificial intelligence algorithms, the effects of vegetation, density difference, and the hyporheic zone on mixing characteristics, and the impact of scouring and sedimentation in sediment-laden flow confluence issues.