NOVELTY - Synthesizing chenodeoxycholic acid comprises (i) preparing cholic acid ester, (ii) preparing 3 alpha ,7 alpha -diacetyl-12 alpha -hydroxy cholate, (iii) preparing 3 alpha ,7 alpha -diacetyl-12-oxochenodeoxycholate, (iv) preparing 12-oxochenodeoxycholic acid crude product, (v) preparing chenodeoxycholic acid by adding ethylene glycol, solid sodium hydroxide and hydrazine hydrate into 12-oxochenodeoxycholic acid, refluxing, evaporating, cooling, pouring into water, acidifying, precipitating, filtering, washing to obtain chenodeoxycholic acid crude product, recrystallizing to obtain refined product.    USE - The method is useful for synthesizing chenodeoxycholic acid.    ADVANTAGE - The method: is convenient, economical and environmental friendly; produces high yield; and is suitable for industrial production.    DETAILED DESCRIPTION - Synthesizing chenodeoxycholic acid comprises (i) dissolving cholic acid in alcohol, adding concentrated hydrochloric acid as a catalyst, refluxing, cooling, crystallizing, filtering and washing with methyl alcohol to obtain cholic acid ester, (ii) dissolving cholic acid ester in dichloromethane and triethylamine, stirring and adding acetic anhydride and lutidine catalyst, evaporating the dichloromethane, pouring into water and filtering to obtain 3 alpha ,7 alpha -diacetyl-12 alpha -hydroxy cholate, (iii) dissolving 3 alpha ,7 alpha -diacetyl-12 alpha -hydroxy cholate in ethyl acetate and methyl alcohol using tetrabutyl ammonium bromide and bromide as the catalyst, stirring and adding drops of acetic acid and hypochlorite, evaporating the organic solvent and filtering to obtain 3 alpha ,7 alpha -diacetyl-12-oxochenodeoxycholate, (iv) adding 3 alpha ,7 alpha -diacetyl-12-oxochenodeoxycholate into ethanol and sodium hydroxide solution and refluxing, acidifying the pH, evaporating ethanol and filtering to obtain 12-oxochenodeoxycholic acid product and recrystallizing to obtain the refined product and (v) adding ethylene glycol, solid sodium hydroxide and hydrazine hydrate into 12-oxochenodeoxycholic acid, refluxing for 2 hours, heating to evaporate part of the hydrazine hydrate, continuing heating to 150 degrees C, refluxing, cooling at room temperature, pouring into water, acidifying the pH, separating out the white precipitate, filtering and washing with water to obtain chenodeoxycholic acid crude product and recrystallizing to obtain the refined product.