The invention relates to a preparation method of an anti-reovirus oral recombinant bacillus subtilis spore vaccine for a grass carp. The anti-reovirus oral recombinant bacillus subtilis spore vaccine is prepared in the way that recombinant bacillus subtilis spore on the surface of which a grass carp reovirus immunoprotecive antigen is displayed is coated with a grass carp granulated feed, and the spore has a germination defect and no antibiotic resistance genetic markers. The preparation method comprises the steps that the recombinant bacillus subtilis spore having the germination defect and no antibiotic resistance genetic markers and displaying the grass carp reovirus immunoprotecive antigen on the surface are built, the anti-reovirus oral recombinant spore vaccine in which the grass carp granulated feed coats the recombinant spore is prepared, and the anti-reovirus oral recombinant bacillus subtilis spore vaccine for the grass carp is used for preventing and treating grass carp hemorragic disease aroused by reovirus.