The nonlinear FEM analysis is performed to the problem of large strain nonlinear application for flexible mattress. The element with cloth type option is used to establish the FEM model for the analysis of flexible mattress. The simulation can produce correct profile of deformation, accurate distribution of stress and strain, meanwhile taking account of geometric nonlinear from large strain. The results of the paper are compared with those from the theory and in-situ test. Some valuable conclusions are made from the results analysis.