The invention relates to a method and device for preparing functional nanoparticle/bacterial cellulose composite membranes by an inverted culturing method. The method comprises the steps of preparing a culture medium, carrying out activation and accessing on strains, and carrying out culturing and post-processing on bacterial cellulose membranes, wherein in the step of preparing the culture medium, functional nanoparticles are added. Inverted culturing refers to inversely place a culturing vessel on an oxygen chamber, the culturing vessel and the oxygen chamber are separated by using an oxygen permeating membrane, and a seam between the culturing vessel and the oxygen chamber is sealed. The device disclosed by the invention comprises a base and a culturing vessel, wherein the base is an open vessel with a step at the upper part thereof, the culturing vessel is inversely placed on the step of the vessel, the base and the culturing vessel are separated by using an oxygen permeating membrane, the oxygen permeating membrane and the lower part of the base form an oxygen chamber, and the lower part of the base is provided with an air outlet hole and an air inlet hole. The method and device disclosed by the invention integrate the culturing and functionalization of bacterial cellulose membranes, and are simple in operation, short in cycle and low in cost; and according to the invention, on the premise of not damaging a three-dimensional network structure in a bacterial cellulose membrane, a functionalized bacterial cellulose composite membrane which is good in functional-nanoparticle adsorption property and excellent in performance is prepared.