The nonlinear Finite Element Method (FEM),which is convenient for engineering applications to the pontoon-chain system,is introduced to simulate the large deformation and contact behavior with mud plane for mooring chains.According to the calculation flow given,quasi-static analysis can be carried out to get the displacement and tensile force of pontoon-chain system under external load with water level variation.A practical case,a floating yard of the MSA somewhere,is analyzed to validate the applicability and practical value of the method presented.