NOVELTY - A polymer nanofiber has a shell which surrounds a core. The diameter and length of the polymer nanofiber is 10 nm to 10 microns, and 500 nm to 50 mm, respectively.    USE - Polymer nanofiber is used for functional polymer nanofiber for hybrid polymer nanofiber (all claimed), production of polymer nanotubes and core-shell nanowires.    ADVANTAGE - The polymer nanofiber has high potential in organic solvent adsorption, high performance ion exchange and functional template, and is manufactured by economical process.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) manufacture of polymer nanofiber, which involves carrying out polymerization-reaction of monomers and initiators in solvent (A), dissolving the initiators in polar solvent to obtain polar solution of initiator, dissolving the monomers in the nonpolar solvent to obtain the nonpolar solution of monomer, uniformly mixing the polar solution of initiator with the nonpolar solution of monomer and reacting. The monomers are cationic polymerization monomers, anionic polymerization monomers, free radical polymerization monomers and/or sol-gel reaction monomers. The initiators are free radical initiators, cationic initiators, anionic initiators and/or sol-gel reaction catalysts. The particle size of the initiator is 10 nm to 10 microns, preferably 50-500 nm;    (2) preparation of functional polymer nanofiber, which involves uniformly-mixing the polymer nanofiber with sulfonating agent and reacting, uniformly mixing the polymer nanofiber with comonomer and initiator in solvent (B) and reacting, uniformly-mixing the polymer nanofiber with tertiary amine solution in solvent and reacting, or uniformly-mixing the polymer nanofiber with the added polymerized monomer, catalyst and ligand in solvent and carrying out active graft polymerization reaction. The cationic polymerization monomer is chloromethylstyrene, bromomethylstyrene and/or iodomethylstyrene; and    (3) preparation of hybrid polymer nanofiber, which involves carrying out polymerization reaction of magnetic nanoparticles, monomer, initiator and solvent, absorbing the functional polymer nanofiber with conducting polymer monomer, and reacting polymer nanofiber with oxidant solution, absorbing the functional polymer nanofiber with ethanol solution of oxide, reacting polymer nanofiber with aqueous solution of acid or alkali, or absorbing the functional polymer nanofiber with aqueous solution of metal salt precursor, and hydrolyzing the resulting polymer nanofiber, or polymer nanofiber reacting with reducer.