Abstract: The yttria-stabilized tetragonal polycrystalline zirconia ceramics (Y-TZP) were sintered at temperature of 1 400 ℃ for 5 min under pressure of 15 MPa by using spark plasma sintering. The effects of the raw powder size (from 301.9 nm to 444.8 nm) on the grain size and fracture toughness of Y-TZP ceramics were investigated. The results show that the grain size, the stress-induced phase transformation content and the fracture toughness of the Y-TZP ceramics all increased with the decrease of the powder size. When the powder size was 301.9 nm, the stress-induced phase transformation content and fracture toughness both reached the maximum values, which were 16.18vol% and 7.06 MPa·m1/2 respectively.