Abstract: The high breeding ratio blanket can obtain tritium breeding ratio over 1.5 and energy magnifying factor about 5, the fuel zone has power density more than 50 MW/m3 on average. According to the characteristic of high power density region in the blanket, this paper present the design of a circuitous flow cooling system, which is featured with inserted cooling tubes and the collecting-distributing manifolds. The thermal-hydraulic analysis has been conducted on this cooling system. A 3-D model consisting of the first wall and the fuel zone were established, the CFD code FLUENT were used to simulate the blanket under steady operating condition. As the numerical results show, this conceptual cooling system has a satisfying flow distribution, the pressure drop of coolant in whole fuel zone is 102 kPa, and the outlet temperature is 594 K, which meet the design expectation well. The maximum temperatures of all blanket structures are below the temperature limits, which indicates that the cooling system could carry the fission generated heat out effectively.