Nanostructured polymer blends have attracted significant attention recently. In this paper, the poly(lactic acid) (PLLA)/ethylene-co-acrylic ester-co-glycidyl methacrylate (E-AE-GMA) rubber (80/20) nanoalloys and microalloys were fabricated by melt blending and the structure-property relationships of the prepared alloys were investigated. In the nanoalloys, the rubber domains are homogeneously dispersed in the PLLA matrix with the overall domain size of <100 nm. Such nanoalloys exhibit not only high transparency in the visible region, but also significantly improved ductility and impact strength, compared with neat PLLA. Moreover, the nanodomains in the PLLA matrix enhance the crystallization rate of PLLA drastically. The overall crystallization rate of the PLLA nanoalloy is even higher than that of the PLLA nucleated by talc. In contrast, the PLLA microalloy has a phase structure with the size of the rubber domains being in the micrometer to submicrometer scale. The microalloy is opaque and displays almost the same tensile strength and modulus as the nanoalloy, but much higher impact strength than the nanoalloy.