Polylactide-block-poly(butylene adipate) poly(ester-urethane) (PLAEU) thermoplastic elastomer was obtained by melt chain extending reaction with polylactide-block-poly(butylene adipate)-block-polylactide (PBLA) and hexamethylene diisocyanate (HDI). PBLA was previously prepared with L-lactide and poly(butylene adipate) diol (PBA diol). Experimental parameters including feed ratio, polymerization temperature, and time were optimized. The weight average molecular weight (M-w) of PLAEU surpassed 10(5) g/mol. In contrast to corresponding PBLA, the crystallinity and melt temperature (T-m) of PLAEU decreased, whereas its glass transition (T-g) shifted to high temperature due to the 'pseudoextension' structure of polylactide (PLA) block. Additionally, the crystallinity and T-m of PLAEU were subject to crystallization method and molecular weight. The tensile strength of PLAEU varied from 6.61 to 24.41 MPa and elongation from 190% to 780%. Therefore, the mechanical properties of PLAEU can be regulated by altering the length ratio of PLA to PBA block. The high elasticity of PLAEU can be explained with phase separation mechanism. POLYM. ENG. SCI., 51:908-916, 2011. (C) 2011 Society of Plastics Engineers