Ring-banded spherulites upon crystallization are common in some semicrystalline polymers including poly(3-hydroxybutyri acid-co-hydroxyvaleric acid) (PHBV). In this study, the lamellar assembly of PHBV spherulite in the blend with amorphous poly(vinyl methyl ether) (PVME) has been examined to elaborate the formation mechanisms of banded PHBV spherulites in non-isothermal crystallization process. The behavior of PHBV crystals at different temperatures (Tcs) was recorded and analyzed by using polarized optical microscopy (POM) and scanning electron microscopy (SEM). Under POM, PHBV/PVME (75/25) exhibits double-ring banded morphology with both orange and blue color bands alternatingly arranged along radial direction at a wide temperature range (60 to 100 oC). However, the band spacing and irregularity of the ring patterns on spherulites vary accordingly with Tc from wider-irregular rings at high Tc into slimmer-regular rings at low Tc. To further determine the correlation between crystallization temperature and spherulitic lamellar assembly, SEM was subsequently utilized on fractured samples. Correlations between top-surface banding patterns and interior lamellar assembly under various crystallization temperatures were collected and analyzed for possible formation mechanisms.