A method for coating hollow fiber membranes is disclosed. The method includes preparing a continuous circulating circuit, which includes a membrane contactor module, two liquid reservoirs containing a solvent, two pipeline paths, and at least one injector. The membrane module include a plurality of hollow fiber membranes with an inside area and an outside area, and a housing, where the plurality of hollow fiber membranes are extended inside the housing. The method further include forming a plurality of wetted hollow fiber membranes with the solvent by circulating the solvent through the continuous circulating circuit, filling at least one of the two liquid reservoirs with a coating solution, forming a coating layer on a surface of at least one of the inside area or the outside area of the plurality of wetted hollow fiber membranes by circulating the coating solution through the continuous circulating circuit, and forming a uniform coating layer by injecting the coating solution by the injector for intrusion of the coating solution through the coating layer.