The purpose of this study was to investigate the buckling load of filament-wound composite towers for large scale wind-turbines using the finite element method (FEM). To define the material properties, we used both the effective property method and stacking properties method. The effective properties method assumes that a composite consists of one ply. The stacking properties method assumes that a composite consists of several stacked plies. First, a linear buckling analysis of the tower, filament-wound with angles of $[{pm}60]$, was carried out using the two methods for composite material properties: the stacking method and effective method. An FE analysis was also performed for the composite towers using the filament winding angles of $[{pm}30]$, $[{pm}45]$, and $[{pm}60]$. The FE analysis results using the stacking properties of the composite were in good agreement with the results from the effective properties method. The difference between the FEM results and material properties method was approximately 0~2.3%. Above the angle of $[{pm}60]$, there was little change in the buckling load.