The invention belongs to the technical field of materials, and discloses a bean dreg nano-adsorption freshness protection bag with an antibacterial function and a preparation method thereof. The preparation method comprises the following steps: (1) extracting soluble dietary fibers from bean dregs; (2) preparing nano chitosan; (3) preparing a material liquid: dissolving nano silicon aerogel in glacial acetic acid, adding distilled water, then adding nano chitosan, bean dreg dietary fibers, nano silver particles, glycerol and calcium chloride, heating, and stirring at a constant temperature; (4) adding N-methyl pyrrolidone into the feed liquid prepared in the step (3), stirring at room temperature, heating, and uniformly mixing; and (5) adding the mixture in the step (4) into a twin-screw extruder, extruding into particles, and preparing the obtained particles into the bacteriostatic fresh-keeping bag. The obtained fresh-keeping bag is wide in application range, is applied to fruit and vegetable fresh keeping, shelf life prolonging and surface pesticide residue adsorption, can improve fruit and vegetable quality and food safety, and realizes resource utilization of wastes.