The proliferation of weld and major alloying elements are studied and analyzed by scanning the EDS element of 316L/20G clad pipe weld joint, 316L substrate and 20G steel, and by scanning the electron microscopy and the energy spectrum analysis of 316L-weld zone and 20G steel-weld zone. The results show that the alloying elements in the weld transition layer are diluted by carbon steel, and the carbon atoms spread to the 316L and weld, while alloying elements in the 316L and wire, such as Cr, Ni, penetrate to the carbon steel, but the transition layer plays a good role in isolation, resulting in 316L stainless steel alloy element content is not significantly reduced, maintaining the 316L base metal resistant to corrosion.