The effects of massive laser shock peening treatment (MLSPT) on the microstructural evolution and stress corrosion behavior of the X70 pipeline steel in hydrogen sulfide solutions with different concentrations were investigated by residual stress measurement, microstructural observation and slow strain rate tension test. The results revealed that MLSPT generated nanocrystallines, refined martensite-austenite constituent and nanocarbides in the near-surface layer. The combined effects of MLSPT-induced gradient compressive residual stress and refined microstructures significantly improved the stress corrosion crack (SCC) resistance. Furthermore, the influence mechanism of MLSPT on SCC resistance of the X70 pipeline steel was presented in detail.