The invention discloses a modified
hollow fiber membrane which is composed of a separation layer, a supporting layer and a macroporous layer, the pore diameters of the separation layer, the supporting layer and the macroporous layer are sequentially increased, and a preparation method of the modified
hollow fiber membrane comprises the following steps: weighing polyether
sulfone /
polysulfone, a pore-
foaming agent, a
solvent, an organic macromolecular additive and an inorganic salt additive according to the proportion to prepare a
spinning solution; stirring and dissolving at 80-180 DEG C, centrifugally filtering, defoaming at 40-80 DEG C to obtain a
spinning solution, carrying out coagulating bath on the
spinning solution, molding, cleaning, stretching and
drying to obtain the modified
hollow fiber membrane. According to the preparation method, micromolecular inorganic salt pore-forming agents with different concentrations are added into a spinning solution and a coagulating bath, and interaction among inorganic salt, a
polymer and a
solvent is utilized, so that an inner
skin layer structure and an outer
skin layer structure of the hollow
fiber membrane are adjusted, and a unique three-layer structure of a separation layer, a supporting layer and a macroporous layer is formed; the hydrophilic performance is stable, and the clearance on middle molecules is improved.