The invention discloses a polypropylene material with low density and low diffusivity. The polypropylene material comprises the following components in parts by weight: 70-90 parts of polypropylene resin, 0.1-10 parts of elastomer, 3-10 parts of filler, 1-5 parts of deodorant, 1-5 parts of assistant master batch and 1-2 parts of foaming agent, the alloy material has the advantages of favorable flowability, low density and higher rigidity and toughness, and can satisfy the performance requirements for thin-walled automotive upholstery. The invention also discloses a preparation method of the material. The preparation method comprises the following steps: S1, weighing raw materials; S2, conveying polypropylene resin and an elastomer into a double-screw extruder through a main feeding assembly, uniformly mixing a deodorant and the auxiliary master batch, conveying the mixture into the double-screw extruder through an auxiliary feeding assembly, conveying a filler into the double-screw extruder through a side feeding assembly, mixing, melting, extruding, bracing, cooling and pelletizing to obtain an intermediate product; and S3, performing devolatilization treatment on the intermediateproduct to obtain the low-density and low-emission polypropylene material, and the preparation method is simple in process, easy in condition control and suitable for large-scale production.