Abstract: To solve the dynamic effect of blocking and permeate water under the scouring effect of mudflow on flexible protection project. In this paper, a coupled S-ALE-FEM calculation method considering the water blocking and permeability effect of mudflow flexible protection process is established. The equivalent thin film unit of the ring network considering the water-blocking-permeability effect is established, according to which the Euler-Lagrange coupling algorithm based on S-ALE and Ergun formula is proposed to realize the equivalent water-blocking-permeability quantification calculation of the dense curved beam-like metal ring network mudslide protection process. The kinetic analysis of the whole process of mudflow flexible protection is carried out in conjunction with the USGS mudflow flexible protection model tests, the results are compared with the test results. The study shows that: the coupled method proposed in the paper can reproduce the full process inversion of debris flow impact, height climbing and infiltration accumulation; compared with the test, the maximum errors of debris flow accumulation height and accumulation width are 11.9% and 10.3%, respectively, and the maximum difference of debris flow slurry passage is 3.2%; compared with the test, the dynamic response of key components of the flexible protection system, the maximum errors of right side anchor rope, left side anchor rope and mesh Compared with the test, the errors of the time course curves of the key components of the flexible protection system are 3.2%, 16.4% and 14.4% respectively. Compared with the two theoretical algorithms that do not consider the water blocking effect, the accuracy of the calculation results of the peak debris flow impact force and the difference of debris flow slurry passage are improved by 4.69% and 17.50% at maximum. The S-A-F coupling method proposed in the paper solves the design and calculation challenges of mudflow flexible protection engineering.