Abstract: The high temperature corrosion behavior of 316H stainless steel base metal and weld in simulated coastal atmospheric environment was studied by high temperature corrosion test at 520 ℃ for 3 000 h. The morphology and composition of corrosion products were observed and analyzed by scanning electron microscopy, energy dispersive spectrometer and X-ray diffractometer. The corrosion mechanism was discussed. The results show that the corrosion mass increase curves of the weld and base metal conformed to the parabolic law. After 3 000 h of high temperature corrosion, the corrosion of base metal and weld samples was slight, and the oxide layer was dense and without spalling. The main component was (Cr,Fe)₂O₃, and the corrosion rates were 0.44 and 0.61 μm/a, respectively, both of which were less than 0.001 mm/a, all of which belonged to the complete corrosion resistance level. The corrosion rate of the weld sample was slightly higher than that of the base metal because of the higher content of Cr and Mo in the base metal.