The invention discloses an insulation waterproof cable wire sheath for spaceflight and a preparation method thereof, wherein the preparation method comprises the following steps that (1) under the condition of solvent existence, silicon powder and a silane coupling agent are mixed and dried to prepare modified silicon powder; (2) the modified silicon powder prepared in the first step is mixed withethylenediaminetetraacetic acid disodium salt, epoxy resin and nano silicon dioxide to prepare a mixed material; (3) nitrile rubber, butadiene rubber, the mixed material prepared in the second step,tetramethyl thiuram disulfide, stearic acid, nanometer calcium oxide particles, curing agents and promoting agents are mixed and smelted and are then subjected to extrusion molding to prepare the insulation waterproof cable wire sheath for spaceflight. Good waterproof and insulation performance is realized.