The invention discloses a detergent for metal products. The detergent comprises an ultra-low interfacial tension surfactant, lactic acid, an emulsifier, an acidic detergent, an acidic corrosion inhibitor, a penetrant, coconut diethanol amide, isothiazolinone, tea oil/tea seed powder, an organic solvent and sorbitol. The weak acid detergent has the advantages of favorable cleaning effect and no foam, can easily remove animal oil, mineral oil, heavy engine oil, butter and other thick oil stains on the metal surface, and can form a continuous water film on the cleaned workpiece. The detergent has the characteristics of no phosphorus, no pollution and no residue, and can satisfy the environment-friendly-three waste discharge requirement. The detergent has high solubility, can not become stratified or precipitate after being place for a long time, and has high stability.