To balance the specific surface area and porous structure of nanofibrous heterogeneous Fenton catalyst for therapid transfer of dye molecules during dye-containing wastewater treatment, a polyacrylonitrile nanofiber with bimodaldiameter distribution (n-PAN-D) was prepared and amidoximated, followed by coordinating with Fe3+ ion (Fe-AO-n-PAND). The modification and coordination process hardly changed the fiber morphology and bimodal diameter distribution ofnanofiber membrane. The amidoximated degree of n-PAN-D increased with the increase of the diameter difference, and thecoordination ability of amidoximated n-PAN-D decreased with increasing the diameter difference. Fe-AO-n-PAN-D hadbetter catalytic activity than those with similar thick or thin nanofiber diameters due to the rapid mass transfer of dyemolecules in the catalyst. The possible oxidation and degradation pathway of Reactive Red 195 in the Fe-AO-n-PAN-D/H2O2system was proposed. And the series of reactions may not gradually occur because of the non-selective oxidation of ·OH. Thegood reusability of Fe-AO-n-PAN-D made it potential carrier for heterogeneous Fenton catalyst in wastewater treatment.