Abstract: A grain-grade zirconia toughened alumina ceramic substrate and a method for preparing the same. The ceramic substrate is prepared from alumina power (main phase) and zirconia powder (secondary phase) in a binary azeotrope of anhydrous ethanol and butanone in the presence of magnesia-alumina spinel powder (as sintering aid), phosphate ester (as dispersant), polyvinyl butyral (as binder) and dibutyl phthalate (as plasticizer). In a mixture of the alumina power and the zirconia powder, a volume percentage of the alumina power is 82.44-96.7%, and a volume percentage of the zirconia powder is 3.30-17.56%. The magnesia-alumina spinel powder is 0.1-4.0% by weight of the mixture of the alumina power and the zirconia powder. A particle size ratio of the alumina powder to the zirconia powder is 2.415-4.444.