Abstract. The new kind of bio-based polyamide56 fiber has been synthesized by adipic acid and 1,5-pentanediamine, which was prepared by fermenting a variety of starch. The spin ability, physical and thermal properties of bio-based PA56, PA 6 and PA 66 were evaluated through systematic investigation and measurement. Bio-based polyamide56 resin has been proved to have good spin ability. PA56 have more concentrated distribution of molecular weight than other nylons, which indicated more stable viscosity beneficial for spinning and higher fiber strength. The infrared spectrum showed characteristic amide and methylene absorption peaks of PA56 but different vibration intensities with conventional nylon, which demonstrates different molecular structure. Differential scanning calorimetry combined with thermal gravimetric revealed good heat resistance (the thermal decomposition temperature is 403.7 °C) and high melting-point (254.1 °C) of polyamide56. X-ray diffraction of these fibers were proposed and showed that slightly higher crystallinity of polyamide56 so as to have more regular arrangement of molecular.