NOVELTY - Preparing heavy metal treating agent, involves regulating solid content of municipal sludge to 2-5%, adding defoaming agent to the sludge, regulating pH of the mixture, sterilizing the mixture, cooling the mixture to obtain a culture medium for seed tank fermentation and tank fermentation, inoculating a thermophilic Corynebacterium into a bottle filled with a culture medium to perform shake culture, performing seed tank fermentation, performing tank fermentation, performing post-treatment of fermented liquor, and concentrating the fermented liquor.    USE - The method is useful for preparing heavy metal treating agent for treating waste etching solution.    ADVANTAGE - The method is cost-effective, obtains agent with high additional value, provides new method for recycling municipal sludge, and reduces content of copper ion in waste etching solution.    DETAILED DESCRIPTION - Method of preparing heavy metal treating agent, involves (a) conditioning sludge by regulating solid content of municipal sludge to 2-5%, adding defoaming agent (1-5 g/l) to the sludge, regulating pH of the mixture to 6.5-8 using acid or base, stirring the mixture, sterilizing the mixture, and cooling the mixture to 30-35 degrees C to obtain a culture medium for seed tank fermentation and tank fermentation, where the sterilization is performed at 121 degrees C for 30-60 minutes in seed tank fermentation or tank fermentation, (b) inoculating a thermophilic Corynebacterium into a bottle filled with a culture medium comprising beef extract and peptone liquid to perform shake culture at 28-32 degrees C and 150-250 revolutions per minute (rpm) for 8-12 hours, where the liquid volume in the bottle is 20-40%, (c) performing seed tank fermentation by transferring the thermophilic Corynebacterium shake culture liquor into seed tank (with inoculum size of 1-3%) to perform fermentation culture at 28-32 degrees C, and pressure of 0.02-0.06 MPa for 8-12 hours at speed of 200-260 rpm, where the air flow rate per minute is 1-1.5 times the volume of the culture medium, (d) performing tank fermentation by transferring the thermophilic Corynebacterium shake culture liquor into a fermentation tank (with inoculum size of 2-8%) to culture at 28-32 degrees C and pressure of 0.02-0.06 MPa for 30-42 hours with stirring speed of 180-220 rpm, where the air flow rate per minute is 1-1.5 times the volume of the culture medium, and (e) performing post-treatment of fermented liquor by adjusting the pH of fermented liquor to 4-4.5 using organic acid, concentrating the fermented liquor by high-speed centrifuging process, adding preservative (0.2-2 g/l) into obtained concentrate, stirring the mixture, and packaging the obtained product.