Abstract: The math model for solidification heat-transfer in continuous casting of Φ400 mm round bloom is established.It has been used to make calculation concerning the influences by elements as degree of superheat,withdrawal speed and cooling intensity on bloom temperature,shell thickness and solidification end-point,and thus proper process parameters of secondary cooling for actual site operation are determined.Relevant operation practice has demonstrated that in case of casting Φ400 mm round bloom,with a withdrawal speed up to 0.4~0.6 m/min,the automatically-controlled secondary cooling schedule is satisfactory to the requirements for commercial production of quality blooms.