Abstract: Safety analysis in reactor scale on high tritium breeding blanket based on China Fusion Engineering Test Reactor (CFETR) was carried out with system analysis code RELAP5/Mod 3.4. In view of the complexity of blanket internal structure, an equivalent modeling method for complex flow and heat transfer structures of two cooling systems was proposed, and a heat transfer model between two cooling systems was established. The intact reactor model was completed on the basis, and verified the parameters on the steady-state operation. Then the analysis of loss of flow accident LOFA in fuel zone was performed. The computational results indicate that the sectional decay heat generated by the zone can be taken away by the FW-Tritium breeding zone cooling system, and every thermal-hydraulic parameter is under the limit. The blanket can resist this accident efficiently, and possess excellent thermal safety characteristics. The study also provides a reference for the safety analysis of other blankets in reactor scale.