The poly(lactic acid) (PLA)/ramie fiber biocomposites were fabricated, which exhibited considerable reinforcement effect comparable to the glass fiber at the same loading. The flow-induced morphology of ramie fibers and PLA crystals in the injection molded PLA/ramie fiber biocomposites were investigated, thus revealing its relationship to the mechanical properties. The polarized optical microscopy (POM) and two-dimensional wide-angle X-ray diffraction (2D-WAXD) were used to determine the distribution of nature fibers, which interestingly showed the ramie fibers aligned well along the flow direction over the whole thickness of injection molded parts, instead of skin-core structure. The PLA matrix in its ramie biocomposites had fairly high orientation degree and crystallinity, which was attributed to effective heterogeneous nucleation induced by ramie fibers and local shearing field in the vicinity of fiber surface. Building up aforementioned understanding on flow-induced morphology of PLA/ramie injection moldings, a strong shear flow was applied to enhance the flow effect. Our results showed that classic shish-kebabs and typical transcrystallinity were simultaneously formed in the strong-sheared PLA/ramie fiber samples, which were closely related to formation of row-nuclei induced by the strong shear flow which was further amplified by incorporated natural fibers. Interestingly, unlike the regular ramie fibers in micro-size, some nano-sized ultrafine ramie fibers tended to absorb and stabilize the as-formed row-nuclei, which subsequently grew into the unexpected hybrid shish-kebabs. Consequently, a noteworthy further promotion enhancement in tensile strength, tensile modulus, storage modulus and impact toughness was achieved in the biocomposites compared to the control biocomposite. These results clearly demonstrated that the precisely controlled interfacial crystalline structures of PLA/natural fiber biocomposites under industrial conditions of processing are highly beneficial to the mechanical performances.