NOVELTY - Nano-copper oxide bactericidal composition is obtained by mixing nano-copper oxide powder, surfactant, dispersant and water and grinding for 1-4 hours. The nano-copper oxide powder is prepared by dissolving lignin in deionized water, centrifuging, removing impurities, adding concentrated hydrochloric acid to solution for adjusting pH value to 2-3 to obtain precipitated lignin, drying precipitated lignin, adding pure lignin to deionized water to form lignin solution and mixing lignin solution and copper sulfate solution, stirring, filtering, washing with deionized water and drying.    USE - The nano-copper oxide bactericidal composition is useful in agriculture and medicine fields.    ADVANTAGE - The nano-copper oxide bactericidal composition can be prepared in a simple and environmentally-friendly manner with excellent sterilization effect and without using toxic reagents.    DETAILED DESCRIPTION - Nano-copper oxide bactericidal composition is obtained by mixing 10-40 pts. wt. nano-copper oxide powder, 0.1-15 pts. wt. surfactant, 5-30 pts. wt. dispersant and 30-70 pts. wt. water and grinding for 1-4 hours. The nano-copper oxide powder is prepared by dissolving lignin in deionized water, centrifuging at 10000-15000 rpm for 8 minutes, removing impurities, adding concentrated hydrochloric acid to solution, adjusting pH value to 2-3 to obtain precipitated lignin, adding deionized water to precipitated lignin for dissolving, repeating the above steps to obtain precipitated lignin, drying precipitated lignin to obtain pure lignin, adding pure lignin to deionized water to form 10-50 g/l lignin solution, adjusting pH of lignin solution to 7-11 using 0.5 mole/l hydrochloric acid or 0.5 mole/l sodium hydroxide solution, preparing copper sulfate solution with concentration of 10-30 mmole/l, mixing lignin solution and copper sulfate solution in a volume ratio of 0.5:1-5:1, placing mixed solution in water bath, continuously stirring at 50-100 degrees C for 0.5-5 hours to obtain nano-copper oxide suspension, filtering nano-copper oxide suspension to obtain filter cake, 3 times washing filter cake with deionized water and drying at 20-70 degrees C for 6-24 hours. The surfactant is penetrant JFC, dodecyl dimethyl betaine, polyoxyethylene (10) octylphenyl ether or sodium dodecylbenzene sulfonate. The dispersant is polymaleic anhydride, polyacrylic acid, polyaspartic acid or polyepoxysuccinic acid.