A system for the numerical simulation of 3D temperature and stress fields during casting process was studied, developed and practiced based on finite difference method (FDM) in this paper. An approach where the stress/strain and the heat transfer analysis use the same computational domain was presented, which avoided transferring temperature data between FDM and FEM nodes and elements. A slot-board steel casting was simulated and the calculated results are in agreements with those obtained from practical producing. A system for the numerical simulation of 3D temperature and stress fields during casting process was studied, developed and practiced based on finite difference method (FDM) in this paper. An approach where the stress / strain and the heat transfer analysis use the same computational domain was presented, which avoids transferring temperature data between FDM and FEM nodes and elements. A slot-board steel casting was simulated and the calculated results are obtained from practical productive.