NOVELTY - Preparing lansoprazole crystalline compound comprises: adding ethanol solution into three-necked flask, then adding 2-mercapto benzimidazole and 2-chloromethyl-3-methyl-4-(2,2,2-trifluoroethoxy) pyridine hydrochloride mixture, and stirring by adding sodium carbonate, heating under reflux, washing and drying the resulting solid to obtain intermediate white solid; adding chloroform into three-necked flask, adding intermediate, stirring to dissolve, dropwise adding chloroperbenzoic acid with a mixture of chloroform, reacting, and drying to obtain crude lansoprazole; and refining.    USE - The method is useful for preparing lansoprazole crystalline compound (claimed).    ADVANTAGE - The method has strictly controlled conditions; uses raw materials, which are low in cost and easy to purchase; comprises samples which are basically invariant in related substances and contents under the condition with high temperature and high humidity; produces less by-products, high yield and non-toxic product, and has short production period and further improves the production efficiency.    DETAILED DESCRIPTION - Preparing lansoprazole crystalline compound comprises: (a) adding ethanol solution into three-necked flask, then adding 2-mercapto benzimidazole and 2-chloromethyl-3-methyl-4-(2,2,2-trifluoroethoxy) pyridine hydrochloride mixture, and stirring by adding sodium carbonate, heating under reflux to remove the solvent by evaporation under reduced pressure, washing and drying the resulting solid to obtain intermediate white solid; (b) adding chloroform into three-necked flask, adding the obtained intermediate, stirring to dissolve, cooling the three-necked three necked flask so that the inner temperature of the flask is below 0 degrees C, dropwise adding M-chloroperbenzoic acid with a mixture of chloroform, controlling the reaction temperature so as not to exceed 5 degrees C, reacting for 1-2 hours, then washing and drying, passing into silica gel column, remove the solvent by evaporation under reduced pressure, and drying to obtain crude lansoprazole; and (c) refining crude lansoprazole, where in step (a) the mass ratio of 2-mercapto benzimidazole and 2-chloromethyl-3-methyl-4-(2,2,2-trifluoroethoxy) pyridine hydrochloride is 1:1.7-1.8:0.7-0.8, and in step (b), the mass ratio of intermediate with chloroperbenzoic acid is 0.5-0.6:1.