The polyimide (PI)/polyacrylonitrile (PAN) blend fibers were successfully prepared through a wet-spinning method, derived from the blend of poly (amic acid) (PAA) and PAN precursors in dimethyl sulfoxide (DMSO) solvent. Herein, the effects of thermal treated time and PAN weight ratios on the structures and properties of the PI/PAN blend fibers were systematically explored. The increased thermal treated time favored the imidization of PAA and cyclization of PAN. As a consequence, the optimum mechanical properties of the PI/PAN blend fibers were obtained at a thermal treated time of 10 min with the tensile strength of 1.15 GPa and initial modulus of 50.87 GPa. On the other hand, the combination of PI and PAN facilitated the imidization process of PAA and the formation of ladder structures of PAN, while the optimum mechanical performances were achieved when the PAN weight ratio was 23 wt%. In addition, the PI and PAN macromolecules exhibited good compatibility in the blend fibers with the glass transition temperature around 300 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.