Based on finite element simulation, temperature field, temperature gradient and the evolution of solidification interface of the large hollow turbine blade in the process of directional solidification had been simulated.The experimental results demonstrated that defects were observed at the expanding cross section of casting in directionally solidified nickel-based superalloys. Numerical results indicated that the phenomenon should be attributed to the lower thermal gradient in this zone. Based on these results, one type of the new baffle was proposed.Calculated results reveal that the reasonable design of the new baffle could improve the thermal gradient in the local area. Therefore, the new baffle could more effectively affect the freckle formation and enhanced the mechanical performances of casting.