The poly (D-lactic acid)(PDLA) with various molecular weight was synthesized by using high optical purity of D-lactic acid(D-LA) to prepare the industrial polylactic acid (PLA) /PDLA blends through melt blending. The effects of PDLA content and molecular weight on the Vicar softening temperature(VST), crystal type, crystallization and melting behavior of PLA/PDLA blends were studied by thermal deformation temperature tester, X-ray diffraction(XRD) and differential scanning calorimeter(DSC). The results show that the VST of PLA and PLA/PDLA blends increases from 64.6 ℃ to 152.3 ℃ while the content of PDLA is up to 10%. The smaller the molecular weight of PDLA is, the higher the VST of PLA/PDLA blends is. The results of XRD and DSC show that stereocomplex crystallites (SC) can be formed during melt blending, and the rapid cooling of the blend does not contain PLA homogeneous crystal (HC). It is indicated that the increase of VST in PLA/PDLA blends is mainly due to the increase of SC crystal content; the crystallization temperature (Tc) of the PLA/PDLA blend increases from 95.9 ℃ to 133.4 ℃ while 10% PDLA is added, indicating that SC crystal is an effective nucleating agent for PLA.