The invention discloses a synthesis method for 2-para-fluorobenzoylbut benzamide. The target product 2-para-fluorobenzoylbut benzamide is synthetized by taking 2-para-fluorobenzoylbut benzoic acid, phosphorus oxychloride and ammonium chloride as raw materials under the action that catalyst anhydrous lewis acid is neutralized by a dichloroethane solvent. The synthesis method for the 2-para-fluorobenzoylbut benzamide has the advantages that operating steps are simple; the reaction condition is mild; the energy consumption is low; the producing cost is reduced; the production cycle is short; the product yield is at least 95.5 percent; the product purity is at least 99 percent; and quality requirements of markets on the 2-para-fluorobenzoylbut benzamide are met.