Purpose: Polyacrylonitrile (PAN) fiber was irradiated by gamma rays for crosslinking and the subsequent radiation effect on the changes in properties was evaluated in detail for its potential application in producing carbon fibers.Materials and methods: Wet-spun PAN fiber containing a comonomer (1.1 mol %, methylacrylate) was used in this work.Dimethylsulfoxide (DMSO) was used as a solvent to determine the gel fraction of irradiated PAN fiber samples.The gel fraction can be calculated from the weight of the soluble portion.G values of crosslinking and scission, G(X) and G(S), were calculated from the soluble fraction analysis using the Charlesby-Pinner equation.Differential scanning calorimetry (DSC) was carried out to determine the thermal behaviors of original and irradiated PAN fiber samples.Chopped sample (~5mg) was heated from 100-450 ℃ with a rate of 10 ℃/min in nitrogen and air atmosphere.Mechanical properties of the irradiated and original PAN fibers were measured using a electronic single silk strength tester (LLY-06E) at a constant speed of 20 mm/min.X-ray diffraction diagrams of the samples were recorded within the angle range 2θ =5-50° using CuKα (λ =1.54056 (A)) radiation.Results: Gel fraction determination indicated that gamma irradiation led to the crosslinking of PAN fibers,with G values of G (X) =0.28 and G (S) =0.16 for crosslinking and scission, respectively.Radiation crosslinking led to a reduction in the exothermic peak intensity and moderated the exothermic behavior of the cyclization reaction in nitrogen, as measured by differential scanning calorimetry (DSC).The DSC curves in air exihibited doublet exothermic peak, corresponding to cyclization and oxidation reactions.It is obvious that irradiation had an evident effect on cyclization but had little effect on oxidation.XRD patterns of PAN fibers after irradiation at different doses show that the original crystal structure was not destroyed by irradiation and the highly oriented structure remained unvaried.In addition, within the studied dose range, the tensile strength decreased slightly at low dose and then remained almost unchanged at higher dose, which may result from the crosslinking.Conclusions: Our results indicate that radiation crosslinking could shorten the stabilization time and improve the thermal stabilization process by accelerating the cyclization and regulating the exothermic behavior.In this case, radiation technology has potential application in the production of carbon fibers from PAN fiber precursor.