The electromechanical properties of metallic single-walled carbon nanotubes (SWCNTs) in the electric field are demonstrated with a column shell model in this paper. A hemisphere model is introduced to determine the charge distribution and the local electric field in SWCNTs. By treating the SWCNT as an elastic column shell, the analytical solutions of the charged SWCNT’s axial strain and the radial strain are obtained. SWCNTs with a larger aspect ratio show greater deformation. The greatest radial deformation appears at the end of the tube. The significant axial strain can be induced in CNTs with a large length (around 100 nm) even though the applied electric field is not strong enough. When SWCNTs are fixed at both ends, the radius of SWCNTs becomes small along the axial position.