The moving process ofδ / δgrain boundary during the solidification process of Fe-0.2%C-0.8%Cr has been observed in-situ with confocal scanning laser microscope ( CSLM ), and the establishment of δ/δ grain boundary , the moving mode , the moving speed and the influence of correlative factor were explored in detail.The results showed that the clear grain cannot be formed when δ phase merged during solidification process of the steel if the actual cooling rate was 0.045℃·s-1 .The δ/δgrain boundary with shape of flat will be formed if there is no essential conjunction betweenδphase in a long period of time.The movement ofδgrain boundary cross point drives other δ /δ grain boundaries to move.The moving process is not stable , and the moving rate variation ranges from 0.12to 1.65 μ m ·s-1 .Temperature of the system is the chief factor for influencing the moving rate of δ / δgrain boundary during the solidification.When the temperature fluctuation of system appears , the solidified grain boundary is re-melted , which results in the catastrophic fluctuation of moving rate for δ / δ grain boundary.When the solidification process reaches its end , the average moving rate of δ /δ grain boundary is quicker than that of L / δ interface.The coarsening rate of crystal grain in the melt is slower than that of solidified solid phase crystal grain. The moving process of δ / δgrain boundary during the solidification process of Fe-0.2% C-0.8% Cr has been observed in-situ with confocal scanning laser microscope (CSLM), and the establishment of δ / δ grain boundary, the moving mode, the moving speed and the influence of correlative factor were explored in detail. The results showed that the clear grain can not be formed when δ phase merged during solidification process of the steel if the actual cooling rate was 0.045 ° C. · s- δgrain boundary with shape of flat will be formed if there is no essential conjunction between δphase in a long period of time. movement of δgrain boundary cross point drives other δ / δ grain boundaries to move. moving process is not stable, and the moving rate Temperature ranges from 0.12 to 1.65 μ m · s-1. Temperatures of the system is the chief factor for influencing the moving rate of δ / δgrain boundary during the solidification. What the temperature fluctuation of system appears, the sol idified grain boundary is re-melted, which results in the catastrophic fluctuation of moving rate for δ / δ grain boundary. When the solidification process reaches its end, the average moving rate of δ / δ grain boundary is quicker than that of L / δ interface. The coarsening rate of crystal grain in the melt is slower than that of solidified solid phase crystal grain.