Rigid barriers, including check dams, steel cells and retaining walls, are widely utilized for debris flow mitigation. It has to be said that these rigid structures are generally effective and technical feasible. However, with the enhancement of environmental awareness and innovative materials, flexible barriers have been being created which are very engineering effective, environmental friendly, material saving as well as easy construction in rugged terrain. Although the merits of such structures are summarized in above, the understanding of such barriers are very limited. Most of constructions are just on the basis of engineering experience and largely depend on the factor of safety to eliminate the uncertainties. In this paper, method for debris flow dynamics calibration and conventional ideas for the design of flexible barriers will be illustrated and an advanced method-finite element will be used to analyze the debris flow.