A treatment method for brightening surfaces of copper nickel alloy tubes is provided. The method comprises following eight steps in order: polishing, removing oil, washing with clear water at room temperature after oil removing, pre-pickling, washing with clear water at room temperature after pickling, performing chemical polishing, cleaning and dehydrating. The step of performing chemical polishing includes following three subsidiary steps: preparing a polishing solution, ageing and polishing. The polishing solution comprises 350-430 mL / L of H2O2, 30-50 mL / L of concentrated H2SO4, 10 mL / L of concentrated H3PO4, 17-20 mL / L of C2H2OH, 1-1.5 mL / L of OP-10, and 1 g / L of BTA, with the balance being H2O. The polishing solution is simple in preparation, low in toxicity and harm, high in production efficiency and low in cost. The surfaces of polished copper nickel alloy tubes are bright, beautiful and flat. The method saves treatment time, increases the production efficiency, reduces energy consumption, and improves surface quality of the copper nickel alloy tubes to a certain degree.