Belonging to the technical field of papermaking filler, the invention in particular relates to a modified calcium sulfate whisker and application thereof. The modified calcium sulfate whisker comprises calcium sulfate whisker crystal and an outer uniformly coated starch cross-linking agent shell accounting for 1-8% of the mass of the crystal, and in the starch cross-linking agent shell, the starch and the cross-linking agent are in a proportion of 1:0.05-0.12. Currently, the frequently used fillers in the papermaking industry are heavy calcium carbonate (natural CaCO3 grinding agent), light calcium carbonate (synthesis process), various silicon dioxide grade calcium sulfate crystals and other inorganic fillers, and calcium sulfate is industrial waste, if calcium sulfate can replace calcium carbonate, the social benefits can be greatly increased. And the calcium sulfate whisker can agglomerate after reaching certain size and therefore cannot meet the size requirements of industrial papermaking filler, while the modified calcium sulfate whisker does not agglomerate, thereby giving consideration to the filler size and the interaction effect of the filler and paper fiber. The modified calcium sulfate whisker provided by the invention does not reduce the paper performance as a calcium carbonate substitute.