Abstract: Using code CFX, the integrative cold sodium pool and auxiliary system of CEFR was calculated at steady state case and the thermal design was verified at operation case. The results show that there are thermal stratification phenomena in the cold sodium pool, there exists really the high temperature region at the upper board of the cold sodium pool, and the temperature in the upper zone of bump inhaling plenum is higher than that of other regions. The results provide technical preparation for power up and operation of CEFR.