Abstract. Biomass is a feasible substitute for petrochemicals, providing many of the same chemical building blocks that are required to fabricate durable and high-performance materials. In this paper, the radiation crosslinking of a bio-based polyamide has been investigated over a range of irradiation dose (50-250 kGy) with limited air. The crystallinity variations were studied using infrared (IR) spectroscopy and X-ray diffraction (XRD). The presence of both α and γ phase was seen in all the polyamide fibers at room temperature. Generally, the irradiated BDIS fibers had lower crystallinity levels than that in the unirradiated one (F0) except for the fibers irradiated at the dose of 200kGy (F200). F200 possessed the maximum crystallinity. In addition, gel content of the irradiated fibers was measured. It was concluded that the relation between sol fraction and radiation dose followed the Charlesby-Pinner equation, the ratio of degradation to crosslinking (p 0 /q 0 ) decreased with the increase of molecular weight.