Stable copper and copper oxide nanoparticles were prepared by supercritical hydrothermal synthesis using acidic etching waste solution as raw material. Effect of different alkali additions on the preparation of copper oxide nanoparticles was investigated, verification experiment of the effect impurity removal was carried out. The control mechanism of copper oxide morphology was obtained, and the effect of corrosion on the purity of final products was analyzed. Experimental results show that under optimized parameters, copper and copper oxide nanoparticles prepared by using acidic etching waste liquid as precursor have average particle sizes of 82 nm and 52 nm and purities of 99.4% and 99.2%, respectively, after removal of impurities. Technological process for the pre-treatment of acidic etching waste was established, and the synthesis process of high-purity nano-copper and nano-copper oxide using acidic etching waste as precursor is developed. Finally, the technical economy was accounted on the basis of a pilot-scale continuous plant with a treatment capacity of 480 L/h.