The invention discloses a high-wear-resistance polyurethane elastomer and a preparation method thereof. The high-wear-resistance polyurethane elastomer is prepared from a prepolymer component and a chain extender component, wherein a prepolymer is prepared by the following steps: polyester or polyether polyol and MDI are synthetized into hydroxyl-terminated MDI modified polyol, and then the MDI modified polyol reacts with TDI; the chain extender component is one or a mixture of 4,4'-diamido-3,3'-dichlorodiphenylmethane (MOCA), 3,5-dimethyl-thioltoluenediamine (DMTDA) or diethyltoluenediamine (DETDA). As the composition of isocyanate in the prepolymer is changed, step-by-step synthesis is adopted and a chain extender does not use methyl-bi (3-chlorine-2, 6-diethyl-aniline) (MCDEA), the wear resistance of the elastomer is improved, and the operation process of the elastomer is improved. The elastomer can be used for preparing products such as polyurethane sieve plates, screen meshes and conveying belts in the field of preparation equipment.