The invention provides an environmentally-friendly cable filling material and a preparation method thereof. The material is characterized by comprising the following raw materials by weight parts: 55-59 parts of SG-4PVC resin, 21-24 parts of metallocene linear low-density polyethylene, 3-4 parts of Mo2B5, 4-5 parts of hafnium diboride, 12-14 parts of polyphenylene thioether, 4-6 parts of poly-4-methyl-1-pentene, 32-36 parts of bentonite, 12-14 parts of alumina, 21-24 parts of barium sulfate, 2-3 parts of zinc oxide, 1-2 parts of an accelerator TMTM, 2-3 parts of bis-tetradecene alcohol ester, 2-3 parts of a silane coupling agent KH 550, 1-2 parts of a cross-linking agent TAC, 4-6 parts of epoxy tetrahydro dicapryl phthalate, 1-2 parts of tributyl tin chloride, 10-12 parts of carbon black N 660, 14-17 parts of precipitated silica, and 6-8 parts of modified diatomite. The cable filling material provided by the invention is high in volume resistivity, high temperature resistant, good in insulating property, relatively good in electrical property and good in wear-resistant property.