The invention relates to a lightweight wear-resistant density-gradient foamed sole material and a preparation method thereof. The lightweight wear-resistant density-gradient foamed sole material is mainly composed of EPDM, ethylene-octene copolymer, low density polyethylene, a cross-linking agent, a filling material, a foaming agent and a foaming promoter. On the basis of foaming of EPDM, POE and LDPE and through control of a foaming ratio and density difference values of each layer of materials, a heterogeneous expandable rubber compound composed of a plurality of layers and having quasi-continuously changing performances in the thickness direction of the materials are subjected to one-shot mould pressing, foaming and moulding so as to prepare the foamed sole material, and function gradient differences of density, hardness and wear resistance are realized. Due to gradual change of density, stress concentration is mitigated, and the prepared foamed sole material does not warp. The foamed material has low density at one side close to the vola while the foamed material has high density at one side close to the outer sole, so the foamed sole material has good wear resistance, reduces the weight of the sole and has improved wearing comfortableness.