NOVELTY - A rosuvastatin preparing method involves condensing 4-fluoropropiophenone with ethyl isobutyrate to obtain 1-(4-fluorophenyl)-2,4-dimethyl pentane-1,3-diketone. The 1-(4-fluorophenyl)-2,4-dimethyl pentane-1,3-diketone is heated and reacted with 1-methyl guanidine to obtain 4-(4fluorophenyl)-6-isopropyl-N,5-dimehtyl pyrimidine-2-amine. The 4-(4fluorophenyl)-6-isopropyl-N,5-dimehtyl pyrimidine-2-amine is reacted with methanesulfonyl chloride to obtain N-(5(methyl)-4-(4-fluorophenyl)-6-isopropyl pyrimidine-2-yl)-N-methyl methanesulfonamide.    USE - Method for preparing rosuvastatin.    ADVANTAGE - The method enables preparing the rosuvastatin using less number of process by avoiding two oxidization reactions and one reduction reaction at ultra low temperature, thus improving production efficiency and quality of the rosuvastatin effectively while reducing environmental pollution and production cost.    DETAILED DESCRIPTION - A rosuvastatin preparing method involves preparing condensing 4-fluoropropiophenone with ethyl isobutyrate in an alkali system to obtain 1-(4-fluorophenyl)-2,4-dimethyl pentane-1,3-diketone. The 1-(4-fluorophenyl)-2,4dimethyl pentane-1,3-diketone is heated and reacted with 1-methyl guanidine in cyclization in the alkali system to obtain 4-(4fluorophenyl)-6-isopropyl-N,5-dimehtyl pyrimidine-2-amine. The 4-(4fluorophenyl)-6-isopropyl-N,5-dimehtyl pyrimidine-2-amine is reacted with methanesulfonyl chloride using dichloromethane or tetrahydrofuran as a dissolvent and pyridine or triethylamine as an acid binding agent to obtain N-(5(methyl)-4-(4-fluorophenyl)-6-isopropyl pyrimidine-2-yl)-N-methyl methanesulfonamide. The N-(5(methyl)-4-(4-fluorophenyl)-6-isopropyl pyrimidine-2-yl)-N-methyl methanesulfonamide is bromized with a brominating agent to obtain N-(5-(brooethyl)-4(4-fluorophenyl)-6-isopropyl pyrimidine2-yl)-N-methyl methanesulfonamide. The N-(5-(brooethyl)-4-(4-fluorophenyl)-6-isopropyl pyrimidine-2-yl)-N-methyl methanesulfonamide is reacted with acetaldehyde to obtain rosuvastatin.