A numerical simulation was studied on field of temperature in ceramics by using FDM (Finite Differential Method) during the laser sintering. At first, the heat conduction equations were given, then the boundary condition was given, Finally, the mathematical model of the laser sintering on ceramics was given and the equations were solved by FDM. The simulation program was given by above method, and then the change of field of temperature in ceramics was described by simulation program. The effect of technological conditions on field of temperature in ceramics was analyzed. It shows that the lengthways temperature gradient in ceramics is only relevant to the laser power, and the transverse temperature gradient in ceramics is relevant to the laser speckle radius and the transverse intensity distribution of laser.