A SpitLight2000 nanosecond laser is used to conduct warm laser shock peening (WLSP) experiment on Inconel718 nickel-based alloys. Thermal corrosion test is conducted on the WLSP-samples and untreated samples in mixed molten salt (75%Na2SO4+25% NaCl, percentage mentioned above denotes mass fraction) at 700 ℃. Then the mechanism of WLSP to improve the corrosion resistance of Inconel718 nickel-based alloys is researched by quality detection, X-ray diffraction (XRD) diffraction analysis and corrosion morphology observation. The results show that quality losses in 260 ℃- WLSP- samples after 10 h and 25 h are 18.9% and 17.9% of that in untreated samples. In addition, after thermal corrosion for 10 h, Cr₂O₃ oxidation doesn′t peel obviously on the corrosion surface of WLSP-samples and thus CrS or NiO is not formed. It is indicated that WLSP-samples can prevent implantation of S and thus effectively suppresses thermal corrosion of materials. The reason is that WLSP can lead to grain refinement and γ″ -phase precipitates, which effectively prevents invasion of O and S, and thus improves thermal corrosion resistance of Inconel718 nickel-based alloys.