The material comprises: polypropylene 100, elastomer 6-12, flame-retardant 15-40, nano calcium carbonate 4-10, composite inorganic filler 10-20, erucamid erucyl amide 0.1-1, and pigment 0.1-2. Weight of polypropylene is as basic reference. Specific formulated material of modified flame retardant polypropylene with nano calcium carbonate being interlarded into for sheath tube of power cable is manufactured by mixing materials in formula in high-speed mixer for 8-12 minutes, and granulating the mixed materials by extruding them from a double screw extruder. Temperature of feed cylinder of extruder is 180-220 deg.C, and rotating speed of screw is 400-1200 turns/min. sheath tube is obtained by drawing procedure from the specific formulated material. Advantages are: easy of implementation, lower requirement for manufacturing equipment and stable technique. The material possesses features of high rigidity and intensity, and fire retardation.