The invention discloses a lightweight conductive mortar material and a preparation method and application thereof. The lightweight conductive mortar material comprises, by weight, 100 parts of cement,25-60 parts of conductive porous light aggregate supporting modified agar gel, and 30-45 parts of water. The lightweight conductive mortar may meet the requirements of facing mortar for mechanical properties, has good compressive strength and breaking resistance, has high conductivity uniformity, can maintain high alkalinity in the mortar, can effectively inhibit anode acidification erosion and local deteriorating cracking between a main anode and the mortar caused by anode acidification effect during cathode protection, is capable of stabilizing the alkaline environment, and can provide bothimproved protecting efficiency for a cathode protective system and extended service life for the anode.