The invention provides a cold-resistant flame-retardant covering layer and a preparation method thereof. The cold-resistant flame-retardant covering layer is prepared from the raw materials of cis-polybutadiene rubber BR9000, natural rubber, chloroprene rubber, carbon black, antimony trioxide, chlorinated paraffin, ammonium polyphosphate, a flame-retardant softener, a vulcanizing agent, a vulcanization accelerator, zinc oxide, magnesium oxide, stearic acid, and an anti-aging agent. Compared to prior arts, according to the invention, the cis-polybutadiene rubber BR9000, natural rubber and chloroprene rubber with the properties of high cold flow property and slow vitrification are adopted; and the flame-retardant softener is also adopted, such that rubber crosslink bond softness is improved, and rubber elasticity insufficient of a flame-retardant conveyor belt under dynamic conditions in an alpine region can be made up. Therefore, the flame-retardant covering layer has good flame-retardant property, and also has good mechanical properties under a low temperature condition.