NOVELTY - An efficient repairing agent comprises gypsum, magnesium oxide, diatomaceous earth, carboxymethyl cellulose-melamine formaldehyde resin and hydroxypropyl-modified silicon dioxide/chitosan nanoparticles.    USE - Efficient repairing agent is used for solidifying and stabilizing heavy metal-contaminated soil (claimed).    ADVANTAGE - The efficient repairing agent provides environmentally-friendly heavy metal-contaminated soil with reduced amount of inorganic substance, and without damaging soil properties.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) preparation of efficient stabilized repairing agent, which involves uniformly mixing gypsum, magnesium oxide, diatomaceous earth, carboxymethyl cellulose-melamine formaldehyde resin and hydroxypropyl-modified silicon dioxide/chitosan nanoparticles. Carboxymethyl cellulose-melamine formaldehyde resin is prepared by mixing 250 g melamine, 400 ml aqueous formaldehyde solution with concentration of 37%, and 200 ml water, stirring, adding triethanolamine to adjust pH value to 8-9, reacting at 72 degrees C for 75 minutes, preparing melamine resin prepolymer, mixing 300 g polystyrene maleic anhydride and 120 g paraffin, adding 300 ml water, emulsifying for 30 minutes, obtaining paraffin emulsion, dissolving 300 g cellulose in 20 L water, preparing into carboxymethyl cellulose solution, adding melamine resin prepolymer, placing resultant product in an ice water bath, stirring at 600 rpm, adding paraffin emulsion, stirring at speed of 400 rpm at 85 degrees C, adding acetic acid solution to adjust pH value to 3-4, forming suspension, adding sodium hydroxide solution to adjust pH value to neutral, cooling to room temperature, washing, filtering under reduced pressure, freezing, and drying; and    (2) usage method of efficient stabilized repairing agent, which involves adding efficient repairing agent to heavy metal-contaminated soil. The amount of efficient repairing agent is 1-10 wt.% based on amount of heavy metal-contaminated soil.