The invention provides a preparation method of vimodegil. 2-chloro-5-nitroacetophenone is used as a raw material; 5-oxo-5-(2-chloro-5-nitrophenyl) n-valeraldehyde is prepared through an addition reaction between 2-chloro-5-nitroacetophenone and acrolein, then 5-oxo-5-(2-chloro-5-nitrophenyl) n-valeraldehyde reacts with ammonia and an oxidizing agent in sequence to prepare 2-(2-chloro-5-nitrophenyl) pyridine, 2-(2-chloro-5-nitrophenyl) pyridine is reduced to obtain 2-(2-chloro-5-aminophenyl) pyridine, and 2-(2-chloro-5-aminophenyl) pyridine reacts with 2-chloro-4-methylsulfonylbenzoyl chlorideto obtain vimodegil. The preparation method has the advantages of cheap and easily available raw materials, low cost, short technical process, safe, simple and convenient operation, easily controllable and easily realized reaction conditions, little amount of generated waste liquid, green, environmental friendliness, stable intermediate compounds, high reaction selectivity, high product purity, and high yield, and is suitable for industrial production.