The invention relates to hot-melting type filling paste for an electric cable, which mainly comprises base oil, insulation paste, an oil separation inhibitor, a thickening agent and an antioxidant. The invention further provides a preparation method of the hot-melting type filling paste. The hot-melting type filling paste for the electric cable provided by the invention has the main characteristics of excellent colloidal stability and oxidation stability, heat resistance, weather resistance, no oil separation in systems, small acid value, strong water resistance, no emulsification, excellent high / low temperature performance, and extremely-excellent electrical properties and dielectric properties; the hot-melting type filling paste is mainly applicable to filling air gaps in a cable core of a multi-conductor wire cable, or gaps among electric cable members of an any structure by heating, so as to prevent water or other fluid from flowing or migrating into the electric cable and provide excellent functions in insulation, waterproofing, dampproofing, buffering and the like for the electric cable.