A method for processing waste copper liquid produces high copper content sludge, mainly by recycling a low copper content waste liquid from production of PCB in order to discharge a comparatively higher copper content sludge. First, the waste liquid is classified into an acidic low concentration copper waste liquid, an acidic high concentration copper waste liquid, and an oxidized acidic high concentration copper waste liquid. Then mix with a strong alkali to react and form a cupric oxide sludge that then undergoes dehydration and baking by applicable equipment to remove water and get a higher copper content sludge. It is therefore unnecessary to add other conversion agents to convert copper hydroxide into cupric oxide, thereby turning the valueless low copper content sludge from a waste liquid into a valuable recyclable high copper content sludge.