With a green concept in recent years, synthetic biopolymers based on annually renewable resources hold the basis for the twenty-first-century portfolio of eco-efficient, biodegradable and sustainable plastics. Among currently available biopolymers, poly(lactic acid) (PLA) derived from renewable resources such as starch and sugars arguably represents the most promising category. As a versatile biopolymer, PLA is not only biocompatible and processable with most standard processing techniques, but also presents excellent mechanical performances. Understanding the crystallization behavior may provide theoretical guidance for the processing and manufacturing, which desirably permits the control of morphology and ultimately widens the application of PLA products. During the isothermal and nonisothermal crystallization of PLA in the shear flow, isothermally crystallized PLA cylindrites were exclusively observed upon a crystallization temperature of 120 οC, while nonisothermally crystallized PLA cylindrites could only be achieved through applying shear rates over 5s-1 accompanied by a relatively low cooling rate. It is of great interest that we found carbon nanotubes and a shear flow synergistically assisted crystallization of PLA. The favorable model was further realized during the injection molding, resulting in PLA with much higher crystallinity. Moreover, rich shish-kebab structures of PLA was directly achieved by applying an intense shear flow during the injection molding, which was further facilitated in the presence of poly(ethylene glycol) and demonstrated great benefit for the mechanical performances. Ramie fibers were introduced into PLA for the preparation of high-performance biocomposites, the crystallinity and orientation degree of PLA were both enhanced due to the effective nucleation activity of ramie fibers and strong interactions between the PLA matrix and fibers.