NOVELTY - Preparation of thiabendazole involves mixing and heating o-phenylenediamine and acid condensation reaction in dilute hydrochloric acid, cooling the mixture, precipitating solid, filtering, washing residue with water, obtaining 2-( alpha -hydroxyethyl)benzimidazole, heating, passing into chlorine gas, drying solid, obtaining 2-(1,1-dichloro-acetyl)benzimidazole, adding solvent with anhydrous ethylene glycol dimethyl ether, adding phosphorus pentasulfide, cooling and filtering, adding carbothioamide ethylene glycol dimethyl ether solution and recovering reaction solvent by distillation.    USE - Preparation of thiabendazole used in Fungicide field.    ADVANTAGE - The thiabendazole is efficiently prepared with high yield without polluting the environment, by a simple method.    DETAILED DESCRIPTION - Preparation of thiabendazole involves mixing and heating o-phenylenediamine and acid condensation reaction in dilute hydrochloric acid at 20-30 degrees C to reflux for 10 hours, cooling the mixture to adjust the pH of aqueous ammonia is more than 7, precipitating solid, cooling to less than 20 degrees C, filtering, washing residue with water, drying, obtaining 2-( alpha -hydroxyethyl)benzimidazole, adding?2-( alpha -hydroxyethyl)benzimidazole, water and magnesium sulfate in acetone, then stirring, obtaining mixed solution, adding concentrated sulfuric acid at room temperature, warming at 40-50 degrees C, adding potassium permanganate, reacting at 45-55 degrees C for 1 hour, cooling at less than 20 degrees C, filtering, washing, concentrating filtrate and acetone, filtering solid and washing with water, obtaining 2-acetylbenzimidazole, adding glacial acetic acid as solvent, 2-acetylbenzimidazole and aluminum chloride, heating at 65-70 degrees C, passing into chlorine gas, reacting for 4 hours, stopping chlorine, continuing reaction at 70 degrees C for 30 minutes, cooling, filtering, applying recycled mother liquor, drying solid, obtaining 2-(1,1-dichloro-acetyl)benzimidazole, adding solvent with anhydrous ethylene glycol dimethyl ether, adding carboxamide thiosulfate at 20-30 degrees C, adding phosphorus pentasulfide to control temperature at less than 35 degrees C, warming reaction to 45-50 degrees C for 2-4 hours, cooling and filtering, obtaining carbothioamide ethylene glycol dimethyl ether solution, adding obtained solution, obtaining 2-(1,1-dichloro-acetyl)benzimidazole for 30 minutes, stirring at room temperature, heating at 50-55 degrees C, stirring reaction for 5 hours, and recovering reaction solvent by distillation. The molar ratio of o-phenylenediamine and lactic acid is 1:1.05. The ratio of o-phenylenediamine and dilute hydrochloric acid is 55-108:300-500. The amount of concentrated sulfuric acid mixed solution is 5 wt.%. The molar ratio of 2-( alpha -hydroxyethyl)benzimidazole, water, magnesium and acetone 80-161:50-100:50-100:350-1000. The molar ratio of potassium permanganate and acetone is 90-186:350-1000. The molar ratio of 2-acetylbenzimidazole and chlorine is 1:2. The molar ratio of glacial acetic acid, 2-acetylbenzimidazole and aluminum chloride is 300 g-1200:65-160:2-5. The molar ratio of anhydrous ethylene glycol dimethyl ether, pentasulfide and thiocarboxamide is 300-700:110-185:105-180. The molar ratio of 2-(1,1-dichloro-acetyl)benzimidazole and thiocarboxamide is 1:5.