Polyacrylonitrile (PAN) membranes doped with cross-linked fluorinated block copolymer nanoparticles of poly [(poly(ethylene glycol) methacrylate)-b-poly(2,2,2-trifluoroethyl acrylate)-b-polystyrene] [P(PEGMA)-bPTFEMA-b-PS] with high flux and high adsorption of water-soluble dyes were prepared by phase transition method. The preparation of the PAN membranes includes (1) preparation of P(PEGMA)-b-PTFEMA-b-PS nanoparticles containing the -OH terminal by polymerization induced self-assembly (PISA); (2) preparation of hydrolyzed PAN containing the -COOH moieties with about 1% hydrolysis degree to increase the adsorption of water-soluble dyes; (3) grafting hydrolyzed PAN onto the P(PEGMA)-b-PTFEMA-b-PS nanoparticles through esterification between the -OH terminal and -COOH; (4) formation of modified PAN membranes through phase transition method in the presence of the HPAN-grafting block copolymer nanoparticles. The flux and equilibrium absorption of the modified PAN membranes are 8 times higher and 143% higher than those of the unmodified PAN membranes, respectively. It suggests that modifying PAN membranes by doping with cross-linked fluorinated block copolymer nanoparticles may be a promising method to prepare high performance membranes.