The invention discloses a composite modified activated carbon electrode for removing copper ions in water and a preparation method of the composite modified activated carbon electrode. The preparation method comprises the following steps: (1) screening activated carbon; (2) performing mixing and ultrasonic dissolution on the activated carbon and deionized water, filtering, and drying the activated carbon in a drying oven; (3) performing ultrasonic reaction on the activated carbon in a nitric acid solution, and further drying activated carbon retained by filter paper in an incubator so as to obtain nitric acid modified activated carbon; (4) performing ultrasonic reaction on the nitric acid modified activated carbon in a citric acid solution, further filtering, and drying in the incubator so as to obtain nitric acid and citric acid composite modified activated carbon; (5) uniformly stirring acetylene black, polytetrafluoroethylene and the composite modified activated carbon prepared in the step (4) in ethanol so as to obtain a mixed coating; and (6) uniformly coating a graphite substrate plate with the mixed coating obtained in the step (5), and drying, thereby obtaining the composite modified activated carbon electrode. The preparation method is simple, low in cost and high in electronic adsorption efficiency upon copper ions in water, and the electronic adsorption efficiency upon the copper ions is up to 72.9%.