A novel poly(ester-urethane) with tailor-made structure was prepared by using lactic acid (LA) as starting material through a combination of two facile common reactions. First, a diol was prepared via the esterification between LA and poly(ethylene glycol) (PEG) with low molecular weight. Subsequently, the poly(ester-urethane) was synthesized through the addition polymerization of the LA-based diol and toluene 2,4-diisocyanate with 1,4-butanediol as chain extender. The structure, morphology, and properties of intermediate and the poly(ester-urethane) were analyzed with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography (GPC), X-ray diffraction, differential scanning calorimetry, polarizing optical microscopy, and thermogravimetric analysis. The results indicated that the intermediate was a diol of conjugating quite short lactate sequences with PEG oligomer, and the structure of the poly(ester-urethane) was as expected. The thermal transition, thermal decomposition temperature, and crystallinity of the polymer samples depended on the molecular size of PEG. In vitro degradation property of the poly(ester-urethane) also relied on the molecular weight of PEG. The weight loss percentages varied from 11 to 36% after 12-days immersing in phosphate-buffer saline at 37 degrees C. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013