The invention discloses a cable low heat resistance protection medium with high water content, high stability, low heat resistance, environment protection and effective prevention of termite damage, and a preparation method thereof. The filling medium is prepared by mixing bentonite, fine quartz sand, water and cement, and using a small amount of tartaric acid and sodium sesquicarbonate as additives. As accounted by 100% of mass fraction, the filling medium is preferably prepared by 54%-57% of bentonite, 24%-28% of fine quartz sand, 14%-16% of water, 2.5-3.5% of cement, 0.24%-0.26% of tartaric acid and 0.24%-0.26% of sodium sesquicarbonate. Before condensation, the filling medium has the advantages of better initial liquidity, moderate alkalinity, low bleeding rate and the like. After condensation, compared with traditional material, the filling medium has the advantages of high water content and high stability, and enables the surroundings of the cable to maintain low heat resistancefor long term, the heat resistance is smaller than that of soil, and the hardness is higher, therefore the current carrying amount of the cable is improved, or the running temperature of the cable conductor is reduced.