Abstract: Polyacrylonitrile-block-poly(butyl acrylate) (PAN-b-PBA) was synthesized by atom transfer radical polymerization (ATRP). The structures, thermal property and microphase-separated structures of PAN-b-PBA were investigated using Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC), Thermal Analysis (TA) and Atomic Force Microscopy (AFM), et al. Nanofiber precursors were fabricated by electrospinning. Results showed that block copolymer PAN-b-PBA had microphase separated structure. As-spun nanofiber precursors with uniform diameters and microphase separated structures were obtained. Nanoporous carbon fibers were obtained via stabilization and carbonization of the electrospun precursors. The connexity of the pores can be adjusted by controlling the mass ratio of PAN block to PBA block.