To reveal the erosion mechanism of debris flow bends, this study conducted flume experiments, focusing on analyzing the movement characteristics of debris flow in bends, the erosion patterns of concave banks, and shear stress. The results indicate that: the apex of the bend experiences the most intense erosion, and the erosion intensity in the upstream is significantly greater than that in the downstream. The erosion depth and super-elevation are important factors affecting the instability of soil on concave banks. The dynamic coupling relationship between hydraulic erosion and gravitational erosion influences debris flow erosion. The concave banks in the upper and middle reaches of the bend are high shear stress areas, while the lower reaches are low shear stress areas, and the maximum shear stress occurs near the apex of the debris flow. The flow velocity of the debris flow in the bend varies synchronously with its shear force, with the highest velocity decay rate and the strongest debris flow erosion both occurring at the apex. The circulation within the bend exacerbates the erosion effect of the debris flow.