The invention relates to a method for preparing functionalized regenerated cellulose membranes by using bagasse celluloses, comprising the following steps of: a using the bagasse celluloses as raw materials; b mixing the bagasse celluloses with ionic liquid capable of dissolving the celluloses, and then heating and stirring to obtain cellulose-containing ionic liquid solutions; c uniformly layingthe obtained solutions in a washing tank, drying and then soaking and washing by using deionized water to obtain cellulose gels; d plastifying the obtained cellulose gels in plasticizers; e air drying the plastified bagasse cellulose regenerated membranes and placing in a vacuum drying tank for drying to finally obtain semitransparent bagasse cellulose regenerated membranes; and f coating some surface modifiers on the surfaces of the regenerated membranes to prepare the bagasse cellulose regenerated membranes with specific functions. In the invention, since the ionic liquid is used as a dissolving medium of the bagasse celluloses and any catalysts does need to be added in the reaction process, the method has simple process, and the prepared bagasse cellulose regenerated membranes have the advantages of compact structure, higher tensile strength, better heat stability and no pollution and can be used as mulching membranes or osmotic membranes.