Dendrite growth direction and SDAS（secondary dendrite arm spacing）are dominant effects in controlling solidification quality of electro-slag ingot.Grain growth and distribution of SDAS in the ingot at different casting velocities were simulated by the CAFE method to understand effects on solidification quality

in which moving transfer heat was adopted.The results show that growth direction of columnar grain is controlled by melt pool shape.With increasing in casting velocity

the angular between growth direction and rising direction of melt pool is enlarged

resulting in the deterioration of mechanical properties of the alloy.SDAS is a key point for determining the quality of electro-slag castings

which is the function of partial cooling rate.With increasing in melting velocity

SDAS is decreased

which is beneficial for the decrease of grain segregation and shrinkage porosity（hole）and improvement of casting quality.Casting velocity is dominant in electro-slag process.A higher or a lower casting velocity is harmful for the casting quality.