A method for preparing a cationic electrodeposition coating composition, wherein the method comprises the steps of: respectively dissolving an aminated resin and blocked isocyanate curing agent in organic solvents to prepare respective solutions; mixing the two solutions, and neutralizing the mixture using a neutralizing acid to obtain resin emulsion (i) comprising the aminated resin and the blocked isocyanate curing agent, preparing a pigment dispersion paste comprising a bismuth mixture obtained by mixing a bismuth compound and an organic acid in advance; a pigment dispersion resin; an amine-modified epoxy resin emulsion (ii) comprising an amine-modified epoxy resin; and a pigment, according to any one of the following methods: mixing the bismuth mixture and the pigment dispersion resin, then the obtained mixture being mixed with the amine-modified epoxy resin emulsion (ii), and next, the pigment being mixed in the obtained mixture; or mixing the bismuth mixture, the pigment dispersion resin and the amine-modified epoxy resin emulsion (ii), and then the pigment being mixed in the obtained mixture; or mixing the bismuth mixture and the amine-modified epoxy resin emulsion (ii), and then, the obtained mixture, the pigment dispersion resin and the pigment being mixed; and mixing the resin emulsion (i) and the pigment dispersion paste to obtain the cationic electrodeposition coating composition, wherein the pigment dispersion resin has a hydroxyl value of 20 to 120 mg KOH/g, and the amine-modified epoxy resin has a hydroxyl value of 150 to 650 mg KOH/g. respectively dissolving an aminated resin and blocked isocyanate curing agent in organic solvents to prepare respective solutions; mixing the two solutions, and neutralizing the mixture using a neutralizing acid to obtain resin emulsion (i) comprising the aminated resin and the blocked isocyanate curing agent, preparing a pigment dispersion paste comprising a bismuth mixture obtained by mixing a bismuth compound and an organic acid in advance; a pigment dispersion resin; an amine-modified epoxy resin emulsion (ii) comprising an amine-modified epoxy resin; and a pigment, according to any one of the following methods: mixing the bismuth mixture and the pigment dispersion resin, then the obtained mixture being mixed with the amine-modified epoxy resin emulsion (ii), and next, the pigment being mixed in the obtained mixture; or mixing the bismuth mixture, the pigment dispersion resin and the amine-modified epoxy resin emulsion (ii), and then the pigment being mixed in the obtained mixture; or mixing the bismuth mixture and the amine-modified epoxy resin emulsion (ii), and then, the obtained mixture, the pigment dispersion resin and the pigment being mixed; and mixing the resin emulsion (i) and the pigment dispersion paste to obtain the cationic electrodeposition coating composition, wherein the pigment dispersion resin has a hydroxyl value of 20 to 120 mg KOH/g, and the amine-modified epoxy resin has a hydroxyl value of 150 to 650 mg KOH/g. mixing the bismuth mixture and the pigment dispersion resin, then the obtained mixture being mixed with the amine-modified epoxy resin emulsion (ii), and next, the pigment being mixed in the obtained mixture; or mixing the bismuth mixture, the pigment dispersion resin and the amine-modified epoxy resin emulsion (ii), and then the pigment being mixed in the obtained mixture; or mixing the bismuth mixture and the amine-modified epoxy resin emulsion (ii), and then, the obtained mixture, the pigment dispersion resin and the pigment being mixed; and mixing the resin emulsion (i) and the pigment dispersion paste to obtain the cationic electrodeposition coating composition, wherein the pigment dispersion resin has a hydroxyl value of 20 to 120 mg KOH/g, and the amine-modified epoxy resin has a hydroxyl value of 150 to 650 mg KOH/g.