Carbon nanotube (CNT) is famous for its excellent electrical conductivity, thermal conductivity and mechanics property.Since it was first discovered in 1991, the preparation of CNT has got through the method of electric arc discharge, laser ablation, CVD technique and others.The intrinsic honeycomb network of carbon nanobubes is probably not as perfect as it was initially thought to be however CNTs prepared in any method.Pentagon and heptagon ring present when CNTs come to bending or deformation.These non-hexagon ring impact the energy gap and electronic structure of CNTs.An X-typed carbon nanotube is built by welding carbon nanotube (5,5) and carbon nanobube (8,0) in order to calculate its value of energy gap and electrical structure.energy gap and electronic structure of X-type CNT are computed by the method of density functional theory with the generalized gradient approximations.Density functional theory transforms the complicated N electrons wave function and its corresponding schrodinger equation into simple electronic density function and the corresponding calculation system that simplify the complex quantum computing.The geometric structure and electrical structure of X-typed carbon nanotube are investigated by using the plan-wave pseudo-potential method, with the scheme of generalized gradient approximation revised Perdew-Burke-Emzerhof exchange-correlation potential and ultrasoft pseudopotential.Compared with the carbon nanotube(5,5) and carbon nanotube(8,0), X-typed carbon nanotube of the DOS of the region where the two nanotubes cross, reveals an enhancement of the electronic states at the Fermi energy, and the electrons is distributed in p orbit at the Fermi energy, thus suggesting a strong metallic behavior.It is also notable that the presence of localised donor states in the conduction band is caused by the presence of heptagons.Junction models in terms of local density of states, as those created by irradiation, are described to suggest their importance in electronic device applications.