A method to evaluate the structural safety of lateral buckling load is presented, using FEM analysis for a wind turbine tower with a thin circular wall. Europe, the U.S., and Japan already have long histories of research into wind power due to its high efficiency. The tower structure that supports a wind turbine is one important research area. There are three types of tower that vary by structural composition: a cylindrical tower with a circular cross-section, a jacket tower with a truss structure, and a hybrid tower. This paper investigates an accident involving a 600kW wind turbine that occurred in JeJu, Korea in October of 2010. The results from a numerical analysis are compared with the actual collapse mode observed at the accident. Some buckling modes and wind speeds at which non-linear buckling response occurs are predicted via the arc-length method for a land-based cylindrical stationary tower. The evaluation method is used accident (experiment), analytical, linear and nonlinear finite element method (beam and shell) to analyze the result of predicted buckling load of tower. The result of nonlinear FEM shell model was found to exhibit similar behavior to the accident situation during buckling. It is concluded that this paper provides buckling analysis process and method used for the slender shell structures: the predicted buckling load and analysis methodology. In this paper, The results from the numerical estimation show good agreement with those of the analytical calculation, indicating that the arc-length method effectively improved the convergence. We found out buckling limit load of the accident wind turbine tower and wind speed at buckling point. The result of nonlinear FEM shell model was found to exhibit similar behavior to the actual accident (experiment) situation during buckling. The presented buckling evaluation method will be useful for both static design and dynamic performance evaluation of land-based wind turbines, as well as sea-based wind turbines.