NOVELTY - Preparation of boscalid fungicide comprises reacting 4-chloro-2'-amino-biphenyl with 2-chloronicotinoyl chloride, base and solvent at - 40-50 degrees C where molar ratio of 4-chloro-2'-amino-biphenyl to 2-chloronicotinoyl chloride is 1-5:0.8-2:1 and carrying out recrystallization. The base is triethylamine, N,N-dimethylaniline, N,N-diethylaniline, N,N-diisopropylethylamine, lithium/sodium/potassium carbonate, lithium/sodium/potassium bicarbonate, lithium/sodium/potassium phosphite or lithium/sodium/potassium phosphate.    USE - Method for preparing boscalid fungicide (claimed).    ADVANTAGE - The method is simple, cost-saving and environment-friendly and has high yield. The product has high purity.    DETAILED DESCRIPTION - Preparation of boscalid fungicide comprises reacting 4-chloro-2'-amino-biphenyl with 2-chloronicotinoyl chloride, base and solvent at - 40-50 degrees C where molar ratio of 4-chloro-2'-amino-biphenyl to 2-chloronicotinoyl chloride is 1-5:0.8-2:1 and carrying out recrystallization. The base is triethylamine, N,N-dimethylaniline, N,N-diethylaniline, N,N-diisopropylethylamine, lithium/sodium/potassium carbonate, lithium/sodium/potassium bicarbonate, lithium/sodium/potassium phosphite or lithium/sodium/potassium phosphate. The solvent is methanol, ethanol, propanol, isopropanol, dichloromethane, chloroform or toluene. The 4-chloro-2'-amino-biphenyl is obtained by taking 4-chlorophenylboronic acid and o-nitrochlorobenzene as raw materials and coupling at 50-150 degrees C. The first base is carbonates, bicarbonates or hydroxides of lithium, sodium and potassium. The first and fourth catalyst is nickel chloride, nickel acetate, nickel acetylacetonate, nickel powder/nano nickel powder/reduced nickel powder, bis(triphenylphosphine)nickel dichloride, dibromobis(triphenylphosphine)nickel, tetrakis(triphenylphosphine)nickel, magnetic nanoparticles supported nickel-based catalyst, palladium on carbon, palladium chloride, palladium acetate, tetrakis (triphenylphosphine) palladium, bis(triphenylphosphine) palladium, bis(acetonitrile)dichloropalladium or palladium trifluoroacetate. The second and fifth catalyst is quaternary ammonium salt of formula R4NX. The first and third reaction solvent is N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, dioxane, dimethylsulfoxide, water, tetrahydrofuran, ethanol, methanol, propanol, isopropanol or toluene. The molar ratio of 4-chlorophenylboronic acid, o-nitrochlorobenzene, first base, first catalyst and second catalyst is 0.8-2:1:0.5-3:0.01-5:0.05-0.5. The reducing agent is stannous chloride or iron powder. The second reaction solvent is ethanol, methanol, propanol, isopropanol, water, dimethylformamide, tetrahydrofuran or toluene. The molar ratio of 4-chloro-2'-nitrobiphenyl, reducing agent and third catalyst is 1:2-5:0.1-1. The second reaction solvent is water, methanol, ethanol, propanol, isopropanol or acetone.    R=alkane; and    X=Cl, Br, I, sulfate ion, nitrate ion or phosphate ion.