The work aims to design and simulate the introduction of heterogeneous pollution on site, study the effects of heterogeneous pollution on pipeline welds to solve the phenomenon of unexplained coloring in the pipeline welds of nuclear power plants. Orthophenanthroline color detection method was used to evaluate the heterogeneous iron contamination of 316L stainless steel welds using ER316L welding wire, welding wire doped with iron wire and iron powder, and pure iron wire. Combined with energy spectrum and dynamic potential polarization test, the effect of heterogeneous iron pollution on the structure and corrosion resistance of the weld seam was analyzed. The results showed that the continuous color development on the large surface of the weld was mainly iron oxide and the iron-rich phase in the weld, and the dot-like continuous color development inside the weld was iron oxide slag; under grinding conditions, the weld under the action of no pollution and iron-rich phase prolonged with the air storage time, and the color development degree a gradually decreased; while the dot color development did not change significantly; according to the percentage of the integrated area at the critical chromaticity (ac = 5.3) under the critical red pixel, when the percentage of dot color development was less than 1%, and the color development of band shape was 20%~30%, ac = 5.3, the color development began to appear. In 3.5% NaCl solution, the order of 316L stainless steel welds‘ resistance to electrochemical corrosion was as follows:ER316L + iron powder welds > ER316L welds > ER316L + wire welds > pure iron wire welds. The addition of iron pollution will cause the color development phenomenon to occur more easily, and also reduce the corrosion resistance of 316L stainless steel welds.