The invention belongs to the technical field of chemicals, provides an aluminum and aluminum alloy weakly-alkaline anti-rust cleaning agent and a preparation method thereof, and particularly relates to a weakly-alkaline cleaning agent capable of being used for cleaning pure aluminum and aluminum alloys and having corrosion inhibition and bright effects. According to the weakly-alkaline cleaning agent, grease and oil dirt on the surface of an aluminum product can be effectively removed, and corrosion and color change are avoided. The weakly-alkaline cleaning agent comprises the following components of, by weight, 3-7 parts of an alkaline detergent assistant, 0.1-2 parts of organic carboxylic acid, 0.1-1 part of ternary polycarboxylate, 0.1-2 parts of compound-type low-foam surfactants, 0.5-2 parts of complexing agents, 0.10-3 parts of corrosion inhibitors, and 85-90 parts of water. According to the aluminum and aluminum alloy anti-rust cleaning agent, through the synergistic effect of various alkaline inorganic detergent assistants, the good cleaning effect is achieved, and the problem that as for an existing cleaning agent, due to the high pH valve, corrosion and color change of aluminum materials are caused can further be solved.