Abstract: In order to realize the buckling strength design for the opening door of the large-scale horizontal axis wind turbine（HAWT） tower,the arithmetic combined with the engineering and the FEM was presented.The FEM model of the door was established.The first-order buckling eigenvalues and modes for three different structures were calculated and analyzed.Based on engineering arithmetic,the stress and buckling strength for the sections of tubular tower were obtained.Corrected by FEM results,the tower door with opening buckling strength was checked by engineering arithmetic.The results were compared with those of FEM.The safe design of structure anti-buckling was presented.The arithmetic presented in this paper is feasible and effective for the opening door design in large-scale horizontal axis wind turbine tower.