Dicopper complex Cu2(PDTB)(CIO4)4 was analyzed by electrospray technique under varied conditions in order to investigate the effects of important factors on ionization efficiency. The factors taken into account are spray voltage (Vn), temperature of the drying gas, needle layer distance (Dnl), potential difference between the capillary and skimmer (Vcs), potential difference between skimmers 1 and 2 (Vss), and concentration of analyte. The total ion current increases proportionally with Vn varied from 2.0 to 4.0 kV. The ionic stales are not influenced by the variation of Vn and temperature of the drying gas. Variation in nebulization efficiency caused by varied Dnl appears to influence the detected ions in several ways. Structurally characteristic ions are preserved with Vcs smaller than 50 V, dissociate into fragments of smaller molar mass with Vcs 80 V or greater, and disappear with Vcs 200 V or greater. Vss influences the relative intensities of detected ions by an effect of ion focusing. The dependence of the intensity of detected ions on analyte concentration at 10−4 M or greater is ascribed to the principle of equilibrium in solution.