Structures and electronic properties of gold cluster AuN (N = 2 − 20) are investigated by density functional theory (DFT) using LC-BLYP functional in conjunction with the consistent-correlation pseudo potential cc-pVDZ-PP basis set. The structural evolution and some basic thermodynamic parameters including the binding energy per atom, the second-order difference of energy, and the one-step fragmentation energy are determined and examined in details. Their electronic properties and stability trend are elucidated in terms of the PSM model. The optical spectra of Au6 cluster are also investigated by means of TD-DFT calculations.