Abstract: The beltline region and inlet nozzle of the reactor pressure vessel（RPV） is investigated in this paper. Fracture mechanics finite element model is built, the transient temperature filed and stress filed are analyzed using the detailed thermal engineering analysis result of typical event transients as the input conditions. Combining with the irradiation embrittlement assessment result, the structure integrity of RPV under events is analyzed and assessed adopting the analysis method for the deterministic fracture mechanics. The analysis result shows that brittle rupture would not happen in the interesting region of RPV during the life time of forty years, but attention should be paid to the transients with great changing rate of coolant temperature.