Abstract: Most of the widely used check dams are destroyed by huge impact force of debris flows. Flexible gabion arch dam is thus designed. The structure is made of stone gabions and built in the shape of arch with junked tires attached to the upside. Numerical simulation is performed using the software ANSYS LS-DYNA, focusing on the dynamic response of the structure to the impact of the debris flows. The pore pressure and statistic stability of the above two debris retaining structures are analyzed by MIDAS-GTS. The results indicate that the flexible arch structure can effectively reduce the impact force and mud flow pressure through appropriate deformation.