The invention discloses a self-healing environment-friendly type steel normal-temperature blackening agent which takes a molybdate/sulfur-copper system as a main membrane component and which consists of 12-22g/L of copper nitrate, 14-24g/L of ammonium molybdate tetrahydrate, 8-12g/L of sodium thiosulfate, 18-28g/L of monosodium phosphate, 3-5g/L of oxalic acid, 6-13g/L of nickel sulfate, 3-5g/L of dimethylformamide, 0.5-1g/L of lanthanum oxide, 30-40g/L of aluminum potassium sulfate, 4-10g/L of sodium chloride, 2-6g/L of citric acid, and a surfactant. The blackening agent is high in blackening capability, free of selenium, environment-friendly, low in production cost and simple in process; a steel normal-temperature blackening film layer obtained through blackening has the characteristics that the corrosion resistance and the healing capability are good, a blacking film is free of crack, the film layer is uniform and dark and bright in color, and the adhesion capability and the corrosion resistance are excellent; and the technical indexes of the blackening film layer are that the 3% copper sulfate drop test lasts for 65 seconds (the blackening film layer is not dipped into anti-rust oil), the 3% sodium chloride soaking test lasts for 8 hours, and the binding force is greater than 187 times.