The invention discloses a flame-retardant fireproof cable sheath layer and a preparation method thereof. The flame-retardant fireproof cable sheath layer sequentially comprises an insulating layer, arubber layer I and a rubber layer II from inside to outside, the side wall of the rubber layer II is provided with a plurality of air holes, and the preparation method comprises the following steps: (1) preparing raw rubber; (2) carrying out modification treatment on quartz stone particles; (3) preparing a rubber material II; (4) preparing a rubber material I; and (5) preparing the sheath layer. The cable sheath layer is divided into three layers, and the middle layer is the rubber layer I; natural latex and butadiene styrene rubber are used as raw rubber; lignin contained in additives and isused as a novel rubber reinforcing agent, so a good reinforcing effect is achieved on the butadiene styrene rubber and the tensile strength is remarkably improved; and the silane coupling agent KH550is absorbed to the surface of the quartzite particles, so the bonding property of the quartzite and the rubber material is improved, the bonding force between the quartzite and the rubber is improved,and the bonding of the quartzite particles is firm.