Math model of heat transfer during solidification of Φ400 mm concasting round bloom of steel 34Mn5V has been established and surface temperature values at controlling location of each secondary zone calculated by the model showed no difference to that measured at production ground. It is obtained with calculation by model that the effect of liquid superheating extent on surface temperature of bloom is minor but the effect of casting speed and secondary cooling intensity on temperature of bloom is larger. Production practice showed that the automatic control secondary cooling system met the requirements of industrial concasting Φ400 mm round bloom with cast speed 0. 4 -0. 6 m/min to get quality cast bloom.