A solid dispersion, a method for preparing same, and a solid preparation including the solid dispersion. The solid dispersion contains (R)-4-amino-1-(1-(but-2-ynylacyl)pyrrolidin-3-yl)-3-(4-(2,6-difluorophenoxy)phenyl)-1,6-dihydro-7H-pyrrolo[2,3-d]pyridazine-7-one or a pharmaceutically acceptable salt thereof, and a carrier material. The carrier material is selected from hydroxypropyl methylcellulose acetate succinate and hydroxypropyl methylcellulose phthalate.