Preparation method of pirfenidone

The invention relates to the technical field of pirfenidone bulk drugs, and provides a pirfenidone preparation method, which comprises: S1, stirring and mixing 2-bromo (iodo)-5-methylpyridine, an organic solvent and an alkali solution, and heating to a temperature of 50-80 DEG C to carry out a reaction; s2, after monitoring that the reaction is finished, extracting a reaction product into an extraction solvent through acid-base extraction; s3, the extraction phase containing the reaction product is concentrated and crystallized, and 5-methyl-2 (1H)-pyridone is obtained; and S4, stirring and mixing the dried 5-methyl-2 (1H)-pyridone, iodobenzene or bromobenzene, anhydrous potassium carbonate or cesium carbonate, a copper catalyst and an organic solvent, heating to 110-120 DEG C, reacting, monitoring until the reaction is finished, extracting into an extraction solvent, and concentrating and recrystallizing to obtain pirfenidone. According to the technical scheme, the azidation reaction in the prior art is avoi