NOVELTY - Preparation of a microelement fertilizer comprises pre-processing a pulping waste liquor in a pretreating tank, adding 2-3 mass% flocculating agent comprising a cationic polyacrylamide modified starch, and adding 2-5 mass% oxidant comprising sulfuric acid (H2SO4) and hydrogen peroxide (H2O2); filtering; flocculent solid filter pressing dehydrating; adding 2-3 mass% Fenton's reagent for 10-15 minutes, adding 1-2 mass% complexing agent, and adding 2-4 mass% settling agent to obtain a complex; and adjusting pH at 6-6.5, and drying.    USE - Method for the preparation of a microelement fertilizer (claimed).    ADVANTAGE - The method realizes environment-friendly clean pulping.    DETAILED DESCRIPTION - Preparation of a microelement fertilizer comprises:    (A) pre-processing a pulping waste liquor in a pretreating tank, adding 2-3 mass% flocculating agent comprising a cationic polyacrylamide modified starch, stirring for 8-15 minutes, adding 2-5 mass% oxidant comprising sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) at a mole ratio of 1.5:2, stirring for 8-10 minutes to obtain a preprocessing liquid, feeding in a filter pool, where the cationic polyacrylamide modified starch comprises 160-170 pts. wt. of 2.5-3% gelatinized starch and 150-160 pts. wt. cationic polyacrylamide, and stirring for 1-1.5 hour;    (B) filtering the pre-treated solution in a filter pool, and separating the flocculent solid and water from the recycling water pool;    (C) flocculent solid filter pressing dehydrating, removing the water in the recycling water pool to obtain a water content of 40-60%, and placing sludge cake in a pre-mixer;    (D) collecting the filtered water in a recycling water pool, adding 2-3 mass% Fenton's reagent for 10-15 minutes to make the organic substance in the water carbonize into carbon, hydrogen, and oxygen, adding 1-2 mass% complexing agent, adding 2-4 mass% settling agent to obtain a complex, pre-mixing the mixed sludge cake and complex to obtain a premix, and measuring zinc (Zn), boron (B), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), and chlorine (Cl), placing the premix in a stirring tank, and stirring; and    (E) setting Mo, Zn, Cu, B, Mn, and Fe at a mass ratio of 1:(16-20):(55-60):(1-1.5):(55-60):(15-18):(330-350), adjusting pH at 6-6.5, and drying to obtain a water content of less than 10%.