Poly (3-hydroxybutyrate) (PHB)/poly (L-lactide) (PLLA)/poly (ethylene-oxide) (PEO) composite Ultrafine Fibers were prepared by solution dry spinning technique. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to characterize the PHB/PLLA/PEO composite Ultra-fine fibers. In all of the spinning conditions investigated, the average diameter of the as-spun PHB/PLLA/PEO fibers was 2.1 μm and increased with increasing the mass ratio of PHB/PLLA. The degree of crystallinity of as-spun PHB/PLLA/PEO fibers increased with increasing PHB content in their blends, and the α-form crystals of PHB and PLLA in as-spun fibers were obtained. When the mass ration of PHB/PLLA in as-spun PHB/PLLA/PEO fibers was 3:1,the structure of as-spun fibers was the skin-core, which PHB formed core of fibers and PLLA form skin of fibers; when the mass ration of PHB/PLLA in as-spun PHB/PLLA/PEO fibers was 1:1, PLLA and PEO were embedded into PHB phase by droplet and febrile morphology to form matrix-fibril structure of as-spun PHB/PLLA/PEO fibers.