The invention discloses a preparation method of ziprasidone hydrochloride semihydrate. The method comprises the steps that: water is adopted as a solvent; ziprasidone base is subject to a reaction with dilute hydrochloric acid; the solution is then refined through organic solvent refluxing; and the resulting solution is vacuum-dried, such that a product is obtained. With the method provided by the invention, the generation of impurities is effectively reduced, therefore the yield is improved. Meanwhile, the volatilization of hydrochloric acid gas is effectively reduced, such that the method is environment protecting.