Al2O3-ZrO2-SiO2 material (Also known as AZS) is a very important class of refractory, and plays an important role as high temperature structural ceramics. High stress in the edge of the casting is a major cause of fracture of the product. In this paper, the thermal and mechanical stresses were calculated by finite element method under cooling process. Also, the preheat temperature, thermal conductivity of mold material and thermal convection coefficient known as the influencing factors of thermal stress and decreasing stress measures have been studied. Calculation results indicate the peak stress can be lowered by elevating the preheat temperature, thermal conductivity of mold material can not change the peak stress but influence the changing speed.