Polycarbonate urethane (PCU) was synthesized using polycarbonate diol (PCN), 1, 4-butanediol (BD), and 4,4'-methylene bis(phenyl isocyanate) (MDI) as starting materials by both the melting one-shot method and the solution pre-copolymerization method, respectively. It was then characterized by Fourier transfer infrared spectroscopy (FT-IR), tensile test, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). The results show that the tensile strength increases as the content of the hard segment increases. The decomposition upon heating was observed in two stages i.e. decompositions of hard and soft segments. There is an obvious soft-hard glass transition temperature area, which proves the existence of the micro-phase separation structure. The micro-separation phenomenon becomes more obvious as the content of the hard segment increases. The maximal distance of the hard segment micro-domain is estimated to be 2.932 nm from SAXS results. The PCU synthesized via the solution pre-copolymerization method has better mechanical performance and micro-phase separation structure.