The invention discloses a preparation method of a layer-by-layer self-assembled hollow 
fiber forward osmosis membrane. The preparation method comprises the steps of: preparing hollow 
fiber forward osmosis base film, modifying hollow 
fiber ultrafiltration base film, repeating layer-by-layer 
assembly of polycation and polyanion 
layers, performing interface cross-linking 
polymerization for preparinga selective functional layer, conducting moisturizing, and carrying out treatment and storage so as to prepare the layer-by-layer self-assembled hollow fiber 
forward osmosis membrane. The surface of the hollow fiber self-support base film which is prepared by using a 
phase conversion method is activated firstly, layer-by-layer 
assembly of polycation and polyanion is repeated on the surface of thefilm so as to form an functional polarization layer for an 
electrolyte solution, and the 
polyamide selective layer is prepared through interfacial chemical cross-linking 
polymerization. The prepared hollow fiber forward 
osmosis membrane has a controllable thickness and an internal polarization layer with a high charge capacity, and the internal 
concentration polarization phenomenon can be alleviated effectively during the forward 
osmosis process; therefore, the hollow fiber forward 
osmosis membrane can simultaneously obtain 
high flux and low reverse salt flux, has high 
filtration separation efficiency, easy cleaning and a long service life, and can be widely applied to 
seawater desalination and concentration and 
desalination of brine.