The effect of the starting material powder preparation methods and their influence on the density, phase composition and strength of mullite - zirconia ceramics were investigated and compared. The conventional planetary ball milling process for different time and hydrothermal method to prepare the starting powder were used. Examination of the bulk density, compressive strength and flexural strength befor and after thermal-shock of ceramic samples sintered at temperatures 1300 - 15000C led to the following findings: - density is largely affected by the milling time of conventionally prepared powders, as well as by hydrothermal preparation method; the longer milling time results in higher density of ceramic samples obtained; hydrothermally prepared powders – contrary cause lower densification degree/density of ceramic samples at the same temperature; - with these results correlate the mechanical properties of sintered ceramic samples – decrease of the particle size lead to the growe of the compressive strength to the value up to 170 MPa and also the flexural strength after thermal shock from 1000 to 200C which has the value 40-45 MPa and tendency to grow with increasing the gradient of temperature. Mullite and also ZrO2 (tetr.) crystalline phases are predominant in samples prepared from conventional powders. For samples from hydrothermally prepared powders along with mullite phase formation instead of ZrO2 tetragonal the ZrSiO4 phase formation is observed.