Abstract: Polyurethane prepolymers were synthesized by isocyanate and polyol, and a series of polyurethane (PU) elastomers were synthesized at room temperature, research the effect of different NCO/OH molar ratio (R value) and Polyol Molecular Weight on porperty of polyurethane elastomers on the basis of without small molecule chain extender and catalyst. The polyurethane elastomers were characterized by Infrared spectroscopy (FT-IR), thermogravimetric analysis (Tg) and mechanical performance test. The reaearch showed that with the increasement of R value, thermal stability of polyurethane elastomers increased and then decreased, tensile strength of polyurethane elastomers decreased and then increased. With the increasement of polyol molecular weight, thermal stability of polyurethane elastomers increased and then decreased, tensile strength of polyurethane elastomers decreased gradually.