The invention belongs to the technical field of manufacturing of precision investment casting mold shells, and relates to a mold shell for precision casting or directional solidification of a TiAl-based alloy and a method for manufacturing the mold shell. In slurry of a surface layer and a critical surface layer of the mold shell involved in the method, alumina sol serves as a binder, and high-purity electric smelting yttrium oxide powder and electric smelting white corundum powder serve as fireproof filler; and at least one of Y2O3 and three kinds of yttrium-aluminum oxide, namely, Y3Al5O12, Y4Al2O9 and YAlO3, serves as ingredients of the surface layer of the mold shell obtained after roasting. The mold shell is manufactured through the precision investment casting technology, and the procedures of mold waxing, slurry hanging, sand spreading, dewaxing, roasting and the like are included. The slurry of the mold shell is stable in performance, good in smearing, hanging and flowing performance and easy to store; the mold shell has the beneficial effects of being high in chemical stability, excellent in high-temperature strength, thermal shock resistance and high-temperature creep resistance and the like; and the TiAl-based alloy obtained through precision casting or directional solidification is smooth in surface, and a pollution layer is thin.