Co-adsorption with molecules that strongly adsorb on metallic surfaces is beneficial in improving the surface-enhanced Raman spectroscopy (SERS) detection sensitivity of some weakly adsorbed molecules or ions. In this paper, the co-adsorption of four deoxyribonucleic acid (DNA) bases: adenine, guanine, cytosine, and thymine with ClO(4)(-), was studied. Factors like adsorption ability, applied potentials, and coexisting anions were examined to illustrate how they affect co-adsorption. We found that the four DNA bases in their protonated forms could co-adsorb with ClO(4)(-). Among them, thymine with the weakest adsorption ability on Au showed the weakest co-adsorption ability with ClO(4)(-). In addition, repulsion from both negative potentials and reduced SERS enhancements of Au substrates at relatively positive potentials led to a decrease in the SERS intensity of ClO(4)(-). Moreover, anions such as Cl(-), NO(3)(-), and SO(4)(2-) were shown to influence the co-adsorption of ClO(4)(-) with adenine based on a dynamic and reversible competitive co-adsorption process. The above results are very helpful in optimizing the SERS detection sensitivity of weakly adsorbed ions or molecules via the co-adsorption method.