The invention relates to a cable wave absorbing layer coating system and a coating method thereof. The system comprises a thread releasing shaft, two coating devices, two sintering furnaces, three guide wheels, a traction wheel and a thread drawing shaft, and each coating device comprises a thread passing mold, a liquid storage tank and a liquid scraping mold, wherein the thread passing mold and the liquid scraping mold are fixed on the bottom and the top of the liquid storage tank via a fastening flange and a rubber sealing ring, respectively; the upper end of the liquid storage tank is provided with a liquid adding hole, and the middle of the liquid storage tank is provided with a transparent window. By adopting the system, a cable is coated twice, and is sintered twice, and a coating liquid is formed by mixing a certain amount of Teflon suspension emulsion, graphene, distilled water and triton; the temperature of each sintering furnace is controlled to be within the range of 180 DEG C-320 DEG C; the traction speed is 10-12m / min. By adopting the system, the low-noise cable wave absorbing layer is coated; by a twice-coating and twice-sintering technology, the wave absorbing layer is coated uniformly and firmly so as to guarantee the cable wave absorbing effect. Meanwhile, the cable wave absorbing layer coating system and the coating method thereof have the characteristics of high coating efficiency, good uniformity and consistence and the like.