In this paper we describe hierarchical nanoporous ultrathin fibers, which are synthesized using an electrospinning technique and the surfactant-polymer cotemplates. Composite fibers with viscoelastic characters resulting from the driving force of surfactants are first organized by electrospinning a solution containing nanostructure-directing agents, nonionic triblock copolymer pluronic 123 and polyethylene oxide. Subsequently. the defined shrinkage and calcination of the composite fibers yielded the corresponding nanoporous fibers. The porous structure, size, and shape demonstrated are very sensitive to shrinkage, and nanopores from 3.8 nm mesopores, up to similar to 450 nm macropores can be prepared in direct proportion to the fibrous shrinkage. Protein adsorption experiments demonstrate that the nanoporous fibers with large pores (40 nm) are favorable for the large-size bovine serum albumin (BSA) protein adsorption, where BSA can quickly enter the large pores. Therefore, the superlong large-pore fibers in the form of macroscopic macroporous membranes have potential applications for large-size protein separation.