Abstract: Aiming to the corrosion phenomenon of 316L stainless steel bolt of seawater pump impeller, the cause of bolts corrosion was analyzed through macroscopic and metallographic inspection, chemical composition analysis, scanning electron microscopy and energy spectrum analysis, and potentiodynamic polarization analysis. The results show that the chemical composition of the corroded bolts didn’t meet the standard requirement, and microcracks existed in the metamorphic layer after sparkle drilling under high pulse current. The existence of residual metamorphic layer further degraded the corrosion resistance. Finally the corresponding suggestion was recommended to enhance the bolts corrosion resistance.