Abstract: The CFD software STAR-CD is used to simulate the normal operating conditions of cold and hot plenums in China Experimental Fast Reator (CEFR). Complex 3-dimension model is established by using porous medium method. The temperature and velocity distributions of cold and hot plenums are given. These results are compared with the data of the thermal designs of CEFR which have been completed. Meanwhile, the influence of the buoyancy forces is analyzed. The results of the calculation are valuable for the CEFR design and accident analysis.