Abstract: Toluene-2,4-diisocyanate-poly propylene glycol (TDI-PPG) prepolymer was synthesized by two-step method with the protection of argon under normal pressure. A small amount of polytetrahydrofuran ether diol (PTMG) and trimethylolpropane (TMP) as chain cross-linker, were mixed with the TDI-PPG prepolymer to prepare a polyurethane resin casting. FTIR was used to analyze the molecular structure of theTDI-PPG prepolymer and the cured products. The mechanical properties of the polyurethane resin castings were tested by the universal testing machine. The results show that the addition of PTMG reduces the activity of the reaction while improves the toughness of PU cured product. When the mass fraction of -NCO in TDI-PPG prepolymer is 24.0wt%, the content of PTMG in chain extension crosslinker is 5wt%, and the isocyanate index (R) ranges from 1.01 to 1.05, the tensile strength is 87.4 MPa, the flexural strength is 104 MPa to 106 MPa, the modulus is 3.51 GPa to 3.60 GPa, the elongation at break is 4.45% to 4.83%