The invention discloses a method for preparing high-purity low-chloride electroplated copper oxide. The method comprises the following steps: taking copper, liquid ammonia and high-purity carbon dioxide as raw materials; preparing stronger ammonia water at first; then pumping high-purity carbon dioxide into the stronger ammonia water; preparing and obtaining carbonated ammonia water through controlling the carbonization degree; achieving reaction between the carbonated ammonia water and copper under a certain air pressure to obtain a copper and ammonia complexing solution; preparing heavy high-purity cupric subcarbonate through heating, ammonia distillation, separation, washing, drying and screening; and heating, calcining and decomposing the heavy cupric subcarbonate to obtain high-purity low-chloride electroplated copper oxide. According to the invention, as carbon dioxide serves as the raw material, the problem that the raw material for producing cupric subcarbonate by adopting a traditional method carries heavy metal ions, chloride ion and other impurities is solved, the reaction speed is increased, the production period is shortened, the production efficiency is greatly improved, the impurity content is low, high purity and activity are realized, and the product can be applied more widely. The method has the advantages of high yield, low energy consumption, little pollution and low cost.