Asymmetry in the electronic structure of low-dimensional carbon nanomaterials is important for designing molecular devices for functions such as directional transport and magnetic switching.In this paper,we use density functional theory to achieve an asymmetric spin distribution in a typical(9,0)carbon nanotube(CNT)by capping the CNT with a fullerene hemisphere at one end and saturating the dangling bonds with hydrogen atoms at the other end[1].