A fire retardant blanket relates to the field of building materials, and particularly relates to the field of fire retardant materials for buildings. The fire retardant blanket consists of three layers, namely an aluminium film, a PET blanket and an expansion flame retardant layer. A wire slot is wrapped by the fire retardant blanket in construction, and the aluminium film is outward, so that a beautiful construction site is ensured. The expansion flame retardant adhesive layer of the fire retardant blanket comprises 55-70% of an adhesive and 30-45% of an efficient expansion flame retardant; and the efficient expansion flame retardant is a carbon fiber-like flame retardant which contains the following raw materials by content (weight percent): 5-10% of N, 5-15% of P and 3-10% of C, so that the flame retardant effect is relatively good.