Abstract: To solve the dynamic effects of blocking and permeating water under the scouring effects of mudflow on flexible protection projects, a coupled S-ALE-FEM method considering the water blocking and permeability effects of mudflow flexible protection process is established. The equivalent thin film unit of the ring network considering the water-blocking-permeability effects is established according to the Euler-Lagrange coupling algorithm based on S-ALE and Ergun formula 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, and the results are compared with the test ones. The study shows that the proposed coupled method can reproduce the full process inversion of debris flow impact, height climbing and infiltration accumulation. Compared with those of the tests, 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%. For comparison between the tests and the dynamic response of key components of the flexible protection system, the maximum time-history errors of right side anchor rope, left side anchor rope and mesh are 3.2%, 16.4% and 14.4% respectively. Compared with those of the two theoretical algorithms not considering the water blocking effects, the accuracy of the calculated results of the peak debris flow impact force and the difference of debris flow slurry passage are improved by 4.69% and 17.50%, respectively. The S-A-F coupling method can solve the design and calculation challenges of mudflow flexible protection projects.