The invention provides a preparation method of candesartan cilexetil, which can solve the problems of low reaction efficiency and low yield in the prior art, and specifically comprises the steps of synthesis and purification, wherein the synthesis is as follows: adding trityl candesartan cilexetil into mixed solution containing C1-C5 alcohol and an organic solvent, raising the temperature for reaction under stirring, cooling to room temperature, filtering, carrying out vacuum concentration and evaporation on the solvent, using toluene to recrystallize, precipitating crystals, filtering, and obtaining a crude product of the candesartan cilexetil; and the purification is as follows: adding the crude product of the candesartan cilexetil into the organic solvent, stirring and dissolving at the room temperature, filtering, using alkaline solution with low concentration to regulate the pH of filtrate to 7.5-8, washing with water till neutral, drying and filtering an organic layer, then carrying out the vacuum concentration and the evaporation on the filtrate, using organic alcohols to carry out primary recrystallization, recovering the filtrate, carrying out secondary recrystallization,merging the products of the primary recrystallization and the secondary recrystallization and obtaining the candesartan cilexetil with higher purity. The method is simple to operate and can avoid thecomplicated operation and the reagent waste caused by column chromatography and other methods, and the yield is higher.