An embodiment of the invention discloses a digital optical fiber combiner and a method for acquiring dynamic masks by combined optical fiber bundles. The digital optical fiber combiner comprises a combined optical fiber bundle module, an optical on-off module and a packaging and protecting module. The combined optical fiber bundle module comprises a first combined optical fiber bundle and a secondcombined optical fiber bundle which are the same in structure and positioned at two ends of the digital optical fiber combiner symmetrically, and each of the combined optical fiber bundles is formedby combination of multiple bundles of covering optical fibers in a preset arrangement mode. The optical on-off module comprises a plurality of connecting cells and pixel switches positioned in slots of the connecting cells, and the connecting cells are as many as half of the total covering optical fibers. Every connecting cell is used for holding the inner end of a first covering optical fiber ofthe first combined optical fiber bundle and the inner end of a second covering optical fiber of the second combined optical fiber bundle corresponding to the first covering optical fiber, and every slot is formed is formed between the inner end face of the first covering optical fiber and that of the second covering optical fiber. The packaging and protecting module is used for packaging connection of the pixel switches and protecting the digital optical fiber combiner. The digital optical fiber combiner is capable of acquiring mask patterns dynamically and increasing a photoetching resolutionratio.