Poly(L-lactide) (PLLA) is a biodegradable crystalline polymer exhibiting good biocompatibility and mechanical performance.One of most important features of PLLA is brittleness.It is reported that the toughness of PLLA can be improved by blending with biodegradable low molecular weight PEO [1-4].On the other hand, since PLLA is a semi-crystalline polymer, its mechanical properties depend very much on its crystallization structure.Therefore, in this presentation, high Mw PEO was selected to blend with PLLA for improving the toughness of PLLA.The crystallization behavior, especially the stretching induced crystallization behavior of the blends, was systematically investigated.