A solid dispersion, a method for preparing same, and a solid preparation comprising 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.