Abstract: Nail-shooting technique is applied to measure shell thickness of typical high-carbon chromium bearing steel GCrl5 240 mm x240 mm casting bloom, and the electromagnetic stirring position at different casting speed is calculated by the solidification law which can determine the length of the liquid core and the solidification coefficient according to the solidification rate 0. 65 and 0.75. Meanwhile, compared with the calculation results of the secondary model of the casting machine, the influence of the casting speed on the quality of the continuous casting bloom is discussed without changing the position of final electromagnetic stirring (9.4 m). And the magnetic stirring strength of the final electromagnetic stirring is measured by using the tesla meter HT201 to determine the optimal process parameters of final electromagnetic stirring. The results show that increased pulling speed from 0. 68 m/min to 0. 75 m/min has better effect； the optimized electric stirring parameters are current 450 A and frequency 8 Hz ； after process improved, the qualified rate of central segregation is increased from original 75% to 92%.