Abstract: The method of ultimate bearing capacity calculation of the arch structure of plastic greenhouse was presented in the research. The nonlinear finite element analysis theory was applied in the method development. Based on the consistent mode imperfection method, the initial defect model was determined by the least order mode of eigenvalue buckling, and the maximum displacement value. Double nonlinear factor was considered in the structure analysis. To calculate the ultimate bearing capacity, the equilibrium path of the load and displacement using arc-length method was traced. The ultimate bearing capacity of the multi-span plastic greenhouse under snow load in the eastern-China was calculated by the method. The calculated result was close to the production-marked bearing capacity , which showed that the method was suitable.