We report a study of the electronic structures and chemical bonding of gaseous [HAuCN](-) and the corresponding neutral molecule using photoelectron spectroscopy and relativistic quantum chemistry calculations. The electron affinity of the neutral HAuCN is reported to be 4.75 eV for the first time. The low-lying excited states of neutral molecule are observed and assigned according to the calculations utilizing a sophisticated electron correlation method incorporating both the scalar and spin-orbit relativistic effects. Our theoretical calculations suggest the geometry will be distorted from linear structure to the bent during the process of detaching one electron from the anion. Various chemical bonding analyses based on theoretical calculations have been performed for the titled complexes, and the apparent covalent natures of interactions between gold and the studied ligands have been verified.