The interfacial compatibilization of immiscible polymer blends is an economic and efficient technique to fabricate desirable materials with synergetic properties. However, the effect of compatibilizer on crystallization of blend is far from well-comprehended due to the complexity of compatibilities among each component, making it difficult to produce blends with high crystallinities. Herein, a new conception, termed as Interfacial Stereocomplex Crystallites (i-SC), is conceived by reactive blending of poly(L-lactide) (PLLA) and poly(vinylidene fluoride) (PVDF) in the presence of the reactive poly(D-lactide) PDLA-based compatibilizer. During blending, both the grafting of PLLA onto the compatibilizer and stereocomplexation of PLLA/PDLA occurred simultaneously at the PVDF-PLLA interface. It is indicated that the i-SC can not only serve as compatibilizer to reduce interfacial tension by selectively entanglement of grafts with corresponding miscible phase, but also efficiently improve increase the crystallization rate of each component. The in-situ formation of i-SC by reactive blending would open up a new horizon to fabricate super-robust and heat-resistant PLA-based blend materials with high crystallinity through industrial reactive processing.