Orthogonal design was applied to analyze the effect of simulation parameters on the thermal field and cooling curve during directional solidification using commercial finite-element analysis software ProCAST. The results show that solidification curves of single crystal superalloy vary greatly with several numerical simulation parameters and are particularly sensitive to the values of the heat transfer coefficient between the mold and test slab casting without core. The predictions of the temperature filed during solidification for slab geometries were compared with experimental results and calculated cooling curves are in good agreement with experimental measurements. The simulation parameters that had the greatest influence on high rate solidification (HRS) casting process simulation results were modified and determined.