The invention provides a sealing and sound insulation structure of an automobile wiring harness via hole. The sealing and sound insulation structure comprises a sealing rubber jacket, an external front wall sound absorption pad and a cowl panel metal plate; the sealing rubber jacket comprises a rubber jacket body composed of a sound absorption pad sealing part and a metal plate sealing part; the middle of the rubber jacket body is provided with a through hole; the rubber jacket body and the external front wall sound absorption pad are fixed to the cabin side of the cowl panel metal plate; the external front wall sound absorption pad is provided with the via hole; the side surface, close to the cowl panel metal plate, of the sound absorption pad sealing part is tightly pressed on the outer side surface of the external front wall sound absorption pad and covers an opening in one side of the via hole; the metal plate sealing part is arranged in the via hole; and the side surface, close to the cowl panel metal plate, of the metal plate sealing part is tightly pressed on the cabin side surface of the cowl panel metal plate. The sealing and sound insulation structure of the automobile wiring harness via hole can be directly installed into the sealing rubber jacket from the cabin side during assembling, the assembly difficulty is greatly lowered, and the assembly time is saved.