Abstract: The fixed shielding platform plays important function in China Experimental Fast Reactor (CEFR), and it’s extremely important to sufficiently cool it. In this paper, CFD method was used to perform three-dimensional numerical research on the cooling system for fixed shielding platform. Flow characteristic and hydraulic design of the cooling system were analyzed detailedly. The optimization suggestions were put forward on the defects in the design. The results show that the cooling system can basically meet the requirements, but some parts need to be optimized. Flow field distribution in horizontal channels will be improved with more uniformly distributed regulating valves. The uniformity of airflow in vertical channels can be improved with two sets of throttles at inlets. The openness of regulating valves should be properly increased to further meet the requirements of flow distribution. This work can provide reference for operation safety of CEFR and design of similar cooling systems in the future.