Abstract: Analyzed are the temperature field and thermal stress field of the centrifugally cast hollow bloom in 21CrMo10 steel under different technological parameters by means of the FE analysis software ANSYS 8.0/ Multipysics. Based on the analysis result and relevant operation result, it is identified that the cause for the axial cracking of the said hollow bloom is the insufficient inner surface coat thickness and the temperature gradient∧10 ℃/mm of the casting mould; and that along with the reducing of the said coat thickness, the molten steel temperature is going up, resulting in a trend of the bloom inner surface thermal stress to increase. Accordingly, the parameters for coating the mould inner surface is further optimized and determined for casting qualified hollow blooms under specific operation conditions.