A first-principles quantum chemistry method, based on the Kohn-Sham density-functional theory, is used to investigate the adsorption of CO and O-2 on small gas-phase gold cluster anions. The saturated adsorption of carbon monoxide on gold cluster anions Au-N(-) (N=2-7) is discussed. The adsorption ability of CO reduces with the increase of the number of CO molecules bound to gold cluster anions, resulting in saturated adsorption at a certain amount of absorbed CO molecules, which is determined by geometric and electronic properties of gold clusters cooperatively. The effect of CO preadsorption on the electronic properties of gold cluster anions depends on the cluster size and the number of adsorbed CO, and the vertical detachment energies of CO-adsorbed gold cluster anions show a few changes with respect to corresponding pure gold cluster anions. The results indicate that the impinging adsorption of CO molecules may lead to geometry structure transformation on Au-3(-) cluster. For the coadsorption of CO and O-2 on Au-2(-), Au-3(-) isomers, Au-4(-), and Au-6(-), we describe the cooperative adsorption between CO and O-2, and find that the O-2 dissociation is difficult on gas-phase gold cluster anions even with the preadsorption of CO. (C) 2004 American Institute of Physics.