Aliphatic polyesters as biodegradable polymeric materials, which were prepared from various constituent monomers, are considered as the most probable counterproposal to solve the environmental pollution problem by disposal plastics. Therefore, many researchers have been carried out in terms of synthesis for new biodegradable materials by employing molecular design concept or modification of well-known aliphatic polyesters such as PHB, PCL, PLLA and PBS to improve biodegradablility, mechanical properties, processability and price competitiveness. It is well known that biodegradability of aliphatic polyesters is strongly dependent on primary structure determined by synthesis process. but in an attempt to study the effects of primary structure on biodegradation, incorrect conclusions might be drawn on the most dominant factor affecting biodegradability regardless of morphological factors and highly-ordered structure. In everyday life, most biodegradable polyesters are used in solid state such as a bulk container, films or fiber. Therefore, the biodegradability of polymers in solid state are significantly influenced by morphological factors and highly-ordered structure such as the crystal shape and size, crystallinity and molecular orientation as well as the chemical structure such as the degree of polymerization, the presence of functional groups, the hydrophilicity/hydrophobicity balance and crosslinking structure. In this paper, the morphological factor and highly ordered structure was evaluated by means of TEM and wide-/small-angle X-ray scattering, and the relationship between these factors and the biodegradability of aliphatic polyesters was examined in detail.