The Chinese helium-cooled solid breeder (CH-HCSB) test blanket module (TBM) is designed to be tested in ITER, and its aim is to validate the feasibility of a DEMO fusion reactor. The thermal-hydraulic transient analysis has to testify that the TBM and its helium cooling system (HCS) will not impact the safe operation of ITER under both normal and accidental conditions. In order to simulate the transient accidents, the TBM and HCS are modeled using the RELAP5/MOD3 system code. The steady-state results indicate that the designed TBM inlet/outlet temperatures are obtained and the temperature of first-wall (FW) structural material is below the limit. An ex-vessel loss-of-coolant accident (LOCA) will induce the melting of FW beryllium armor after ~80 s of LOCA initiation, and some controlling measures have to be taken before melting. The pressurization of the vacuum vessel induced by an in-vessel LOCA is within the allowable value of the ITER design. Because of pressurization of the purge gas system, the tritium extraction system has to be isolated from the TBM quickly when an in-box LOCA happens. Based on the results, the design of the CH-HCSB TBM could be further modified in order to assure the safety of the TBM and ITER, from an engineering point of view.