The invention relates to the technical field of electric transmission lines and discloses a method for preventing corrosion of a down conductor of an electric transmission line. The method comprises the following steps: (1) corrosion protection, namely coating a protective material layer on the surface of the down conductor, and sleeving an outer sheath layer outside the protective material; (2) grounding, namely burying the bottom of the down conductor underground, performing backfill fixation by using soil doped with dried quick lime and tamping; (3) laminating, namely laying a waterproof membrane on the backfill soil, and fixing the periphery of the waterproof membrane with soil. The method disclosed by the invention turns to a primary cause of corrosion of the down conductor, comprehensive protection is performed in multiple aspects, and the corrosion rate of the down conductor can be effectively reduced. Therefore, the service life is greatly prolonged.