The miscibility and morphologies of the 6-arm poly(L-lactide) (6a-PLLA)/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) crystalline/crystalline blends were investigated by differential scanning calorimetry (DSC), optical microscopy (OM) and atomic force microscopy (AFM) in this work. The 6a-PLLA/PHBV blends are partially miscible as evidenced by the two T(g)s which shifted toward each other. Various morphologies were formed in this polymer blends by regulating the blend composition and crystallization temperature. Interpenetrating spherulites were found in 6a-PLLA/PHBA blends under a certain range of crystallization temperatures, and they were analyzed on the basis of birefringence by polarizing optical microscope (POM). It was proved that the growth direction of PHBV lamellae inside the 6a-PLLA spherulites is along the pre-existing 6a-PLLA lamellae. The formation mechanism of the abnormal PHBV spherulite with negative birefringence (neat PHBV spherulite displays positive birefringence) inside PLLA spherulites were discussed in detail. (C) 2015 Elsevier Ltd. All rights reserved.