Geometric structure and excitation energy of the carbon chains H-(C≡C) n -H (n = 3-9,15) were calculated by density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, using ωB97XD exchange-correlation functional in conjunction with the def2-TZVP basis set in the gas phase. Our recent works have found that the ωB97XD/def2-TZVP level can well reproduce the geometry of cyclo carbon derived from experimental observations as well as UCCSD/def2-TZVP calculations , which also makes it robust to the optimization of the current system with the similar sp-hybridized configuration.