Abstract: After 4 a of operation at a nuclear power plant, the downstream pipe of throttle orifice of the fire control system experienced corrosion perforation. By means of material composition analysis, microstructure observation, morphology and XRD analysis of corrosion products, the cause of corrosion perforation was analyzed. The effect of fluid was analyzed by computational fluid dynamics (CFD) software. The results show that the reason for corrosion perforation was tuberculation, and some solutions for this corrosion were proposed to avoid such kind of damage in the future.