Flexible barriers are widely adopted as protection systems against natural hazards, such as rockfalls, landslides and debris flows. They consist of cable nets, steel ropes, brake elements and steel posts to transfer loads to foundations. A key feature is that these structures are light yet they can absorb high energy through the large elasto-plastic deformations and sliding node action. Structurally the flexible barrier system exhibits highly nonlinear behavior. In this paper, a new nonlinear cable element is developed to model brake element while a new sliding element is formulated for simulation of ring nets. Thus, an integrated design method for flexible barrier is developed with deflections and stresses on all elements computed in an incremental-iterative nonlinear analysis. Results by the proposed method are compared with the output by other computational methods and tests and will be reported in this paper. Simultaneously, considerable improvement in reliability and accuracy when compared with over-simplified hand calculation method can be achieved.