The invention discloses a copper cleaning agent and a preparation method thereof. The copper cleaning agent disclosed by the invention consists of an inorganic acid, an organic acid, a surfactant, a penetrating agent, an emulsifier, a defoaming agent, a complexing agent and water. The inorganic acid and the organic acid are compounded, the hazards to health of cleaning workers caused by individual use of the inorganic acid in the traditional cleaning agent are avoided, over etching of a copper workpiece is also avoided, the copper cleaning agent is an environmental-friendly cleaning agent and has a certain oiliness, an effect of cleaning dirt such as oil attached to the surface of a copper part is improved by using the cleaning agent, the cleaning agent solution is acidic, and the oxide skin on the surface of the copper part can be well removed. The cleaning agent prepared by the invention is simple in using method, the copper part only needs to be soaked at normal temperature for 2-5 minutes so as to be cleaned, no greasy dirt residue is left on the cleaned copper part, the color of the surface of the copper part is the copper base color, and the cleaning effect is obvious. The copper cleaning agent disclosed by the invention is simple in preparation method, low in cost and obvious in effect and is suitable for industrial production and application.