a method for preparing a double layered porous hollow fiber membrane and the device and product thereof . the method comprises preparing uncured porous hollow fiber with larger pore diameters as the inner robust supporter of the membrane from thermoplastic polymeric resins by thermal induced phase separation method and then binding an ultra thin coating layer with hydrophilic microfiltration or ultrafiltration function and fine pore diameters prepared on the outer surface of the robust hollow fibers from a solution of the thermoplastic polymeric resins by a coating process using non - solvent induced phase separation method . the double layered porous hollow fiber membranes have such excellent mechanical strength and high water permeation as the membranes prepared by thermal induced phase separation method , such high accurate filtration effect , high hydrophilic effect and high fouling resistance as the membranes prepared by non - solvent induced phase separation method , and high binding force of the membranes between the layers by the above method .