A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols (PCDL), in which PCDL, 1,4-butanediol (BD) and mixture of 4,4-methylenediphenyl diisocy-anate and hexamethylene diisocyanate (HDI) were soft segment, chain extender and rigid segment, respectively. The structures were characterized by using FTIR and 1H-NMR. The thermoanalysis and mechanical properties of products were measured by means of DSC, TG and other systems. The result shows that an important technological thrust is the development of polymeric materials with improved mechanical characteristics. With the increase in content of HDI component, the elongation at break point increases quickly and decomposition temperature decreases. The DSC/TG curves indicate that a phase division exists in the structure of polycarbonate urethanes. Thermal decomposition occurs at two temperature levels because their rigid and soft chain segments correspond to different glass transition domains, respectively. This paper demonstrates that the mechanical properties of polycarbonate urethane can be controlled by changing the ratio of raw materials.