The invention discloses a preparation method of 2-(trifluoromethyl)benzaldehyde, which comprises the following step: under the action of C1-C4 linear chain saturated monobasic fatty acid and C1-C4 linear chain saturated monobasic fatty acid salt of alkali metal, hydrolyzing 2-(trifluoromethyl)dichlorotoluene with water at a temperature of 150-190 DEG C and under a pressure of 0.3-0.78MPa. The invention also discloses a preparation method of an intermediate of 2-(trifluoromethyl)benzaldehyde, which comprises the following steps: performing selective fluoridation of 2-(trifluoromethyl)dichlorotoluene and hydrogen fluoride under the catalysis of antimony halidesantimony halides, wherein the molar concentration is 2-6 times of that of 2-(trifluoromethyl)dichlorotoluene, and the temperature of selective fluoridation is 60-110 DEG C. The preparation methods disclosed by the invention is simple in operation, low in cost, environment-friendly, and high in yield and purity, and can be better applicable for industrial production.