Abstract: A nanocrystalline surface layer was obtained on surface 0Cr18Ni9Ti steel welded joint with a supersonic particles bombarding (SSPB)technology.The microstructure of the welded joint surface was analyzed by means of optical microscope and TEM. The property of the welded joint to resist stress corrosion of H2 S was studied by constant load technique as well.Experimental results showed that after the SSPB treatment, the initial coarse-grained structure in the top layer was refined to the ultra-fine nanocryatal and becomes more homogeneous.The obtained mean grain size in the surface layer within 60 μm is about 10.4 nm.At the same time, the ability of the welded joint to resist stress corrosion of H₂S is enhanced remarkably after the SSPB treatment and no cracks are found after 300 h constant load testing.