TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Property: The molar ratio of the chiral hydroxymethyl epoxypropane, the catalyst, the halo hydrocarbon and the organic pegamine is 1-5:0.01-0.1:1:1-5. The molar ratio of alkali, substituted oxirane compound (I), and cytosine is 1:0.8-1.0:1-1.3. The molar ratio between substituted oxirane compound (I) and magnesium tert-butoxide is 1:0.5-2. The temperature of ethylic acid is 80-100 degrees C. The mass percentage of hydrogen halide is 40-80%, and pH value of hydrogen halide is 2.9-3.6. Preferred Components: The solvent comprises dichloromethane, chloroform, benzene, methylbenzene and/or dimethylbenzene. The catalyst is 4-dimethylamino pyridine. The alkali is chosen from potassium-tert-butoxide, sodium tert-butoxide, lithium tert-butoxide, potassium carbonate, cesium carbonate, sodium hydride or lithium hydride. The reaction solvent comprises N,N-dimethylformamide, N,N-diethylformamide, N,N- dimethylacetylamide, dioxane an/or dimethylsulfoxide. The cleaning solvent comprises methyl formate, ethyl formate, methyl acetate, acetonitrile, ethyl acetate, ethyl propionate, dichloromethane and/or chloroform. The alcohol is methanol or ethanol. The acid is chosen from formic acid, ethylic acid, propionic acid, benzoic acid, toluenesulfonic acid or water-containing crystal of toluenesulfonic acid. The organic pegamine is chosen from triethylamine, N,N-dimethylaniline or N,N-diethyl aniline. Preferred Process: The method further involves performing a nucleophilic substitution reaction between cytosine and substituted oxirane compound (I) with a reaction solvent at a temperature of 50-140 degrees C to get substituted prrimidine compound of formula (II) after removing a proton in the solvent using magnesium tert-butoxide at temperature of 20-120 degrees C to get substituted prrimidine compound of formula (III). The method further involves performing a nucleophilic substitution reaction of p-benzenesulfonyloxymethyl phosphoric acid diethylester while reducing the pressure and distilling the solvent after neutralizing by acid. The solvent is cleaned using a cleaning solvent and dried to get substituted oxirane compound (I). The method further involves performing a de-protection reaction of substituted oxirane compound (I) under presence of ethylic acid at a temperature of 70-120 degrees C. The pressure is reduced and the solution is distilled, cleaned, filtered and concentrated to get substituted oxirane compound (I). Substituted oxirane compound (I) is reacted with hydrogen halide aqueous solution of 10-80% at a temperature of 20-120 degrees C while adjusting pH value of the solution to 2-4 to separate a solid. The solid is recrystallized by alcohol or water to get cidofovir, where the hydrogen halide comprises hydrogen chloride, hydrogen bromide, or hydrogen iodide, and the alcohol is liquid alcohol at the temperature less than 50 degrees C.