A 3D thermal-mechanical finite element model for laser bending of Al2O3 ceramic slice is established with the ABAQUS code. Based on the fields of temperature, stress-strain and displacement from the simulation, the forming mechanism of laser bending of ceramic slice is investigated. The simulated results of different thicknesses are compared with each other, as well as the influence of specimen thickness on the fields of temperature, strain-stress and displacement. It is observed that as the thickness increased, the temperature on the bottom surface may not reach the plastic-turning temperature and the magnitude of the surface residual stress may increase. Through the analysis, it is found that the optimum thickness is between 0.18 mm and 0.31 mm under the specified processing parameters.