Terpoly (ester-ether) (PBT-co-PTMG) was prepared by melt poly-condensation with dimethyl terephthalate (DMT), l, 4-butandiol (BDO), poly(tetramethylene oxide)glycol (PTMG). The molecular structure and molecular weight of the polymers were presented by FT-IR、1H-NMR and GPC， the thermal properties were measured by DSC and TG，The results show that: 1) The Molecular Weight of Terpoly (ester-ether) synthesized from PTMG as the soft segment with the molecular weight of 2 000 and 1 000 is relatively higher than that of 3 000. 2) Both the melting point and degrading temperature of Terpoly (ester-ether) synthesized from PTMG with the molecular weight of 3 000 is lower than those prepared form PTMG with the molecular weight of 2 000 and 1 000.