The challenge to resolve the conflicts between strength and toughness of polylactide (PLA) is still obstacles for wider applications. In this work, intense flow field was applied to regulate crystalline structures of PLA and phase morphology of PHBV. By such intense flow field, a unique hierarchic structure assembled by amorphous PHBV due to lacks of nucleating agents and abundant microfibrillar crystalline superstructure as a strong building block was successfully achieved. Once introducing an intense flow field, amorphous PHBV flexible phase changes the crystallization behavior of PLA significantly: PHBV can not only retard the relaxation of PLA chains which can effectively prevent the collapse of established crystalline fibrils, but also accelerates the crystallization of PLA which induce abundant microfibrillar crystalline superstructure. As a result, the composites exhibited exceptionally simultaneous enhancement in strength and ductility. Thus, this strategy paved a simple and effective way to fabricate high performance PLA-based products via regulating hierarchical structure of blends. Keywords: Polylactide, brittleness, poly(3-hydroxybutyrate-co-hydroxyvalerate), intense flow field, hierarchic structure