The invention discloses a method for synthesizing a dialkyl hydrogenated nopyl benzyl quaternary ammonium salt compound, and antibacterial application of the compound. Dialkyl hydrogenated nopyl amine and a benzyl halide are directly subjected to one-step synthesis to obtain dialkyl hydrogenated nopyl benzyl quaternary ammonium salt; in an organic solvent, the dialkyl hydrogenated nopyl amine and the benzyl halide (chlorine, bromine and iodine) are fed into a conical flask according to a material ratio, wherein the conical flask is provided with a stirrer and a condensate backflow device; heating is performed for reaction; the reaction temperature is controlled to be 100 to 150 DEG C; the reaction time is controlled to be 1 to 3d. After reaction, products are subjected to suction filtration, washing, recrystallization and vacuum drying; seven dialkyl hydrogenated nopyl benzyl quaternary ammonium salt compounds are obtained through synthesis; the seven dialkyl hydrogenated nopyl benzyl quaternary ammonium salt compounds have a good inhibition effect on phoma citricarpa and colletorichum glecosporioides. The raw materials are rich; the operation is simple; the reaction is simple; the reaction conditions are mild; the purification post treatment is simple. Compared with a traditional antibacterial agent, the antibacterial compound has the advantages of simple structure, safety, no toxicity, little environment pollution and the like, and has good application prospects.