The function of the secondary cooling water system of China Advanced Research Reactor is to transmit the heat of systems,such as coolant system,to the final heat sink.The article introduces the func- tion of the secondary cooling water system,the operating conditions,the composition and process of the sys- tem.It also analyzes the parameters for system design,the water treatment for secondary cooling water,the control and monitoring over the system.The design of this system is proper,and it accords with correspond- ing nuclear safety criterion and standard requirements.