The purpose of this study is to estabilish the synthetic condition of polyurhethane elastomer for excellent properties. Polyurethane elastomer which have different NCO percentage and hard segment contents was synthesized by casting method. And the effects of hard segment contents were investigated by analytical methods such as IR, DSC, etc. [NCO]/[OH] ratio was proper at the range 1.02∼1.05. By IR absorption peak(1250㎝^(-1)) which indicate interurethane hydrogen bond it was confirmed that hard segment were crystallized. Melting point that was determined by DSC showed the effects of hard segment contents, phase mixing and crystalline size.