Abstract: Based on the operation of horizontal continuous casting conducted by Chengdu Seamless Steel Tube Plant, a math simulator for heat-transfer during large-sized HCC bloom solidification has been set up.With the math simulation, changes of the temperature fields of the bloom in the mould and the spray section during heat-transfer thereof and the relationship between such elements as the skull developing law and the liquid core length and casting parameters(withdrawing speed, casting temperature etc.) can be obtained.