A method of Pt deposition on a pre-oxidized 316LN steel surface was developed in an artificial environment, which aims to simulate hydrogenated water chemistry (HWC) condition of the primary loop of PWR and then its effect on the electrochemical behavior in the same environment of the structural material 316LN steel was studied by SEM, XPS, XRD, ICP-AES and linear dynamic polarization etc. At first, all the test steel samples were exposed in 320 ℃water with less than 100 μg·kg^-1 oxygen for 400 h in order to form an oxide scale on the steel surface. Next, the pre-oxidized steel were immersed for 48 h at 150 ℃ to the water with addition of Na₂Pt(OH)₆ to deposit Pt (0, 10, 50 and 100 μg·kg^-1, respectively) on the pre-oxidized steel. Finally, the samples were exposed to 300 ℃ high temperature water with <100 μg·kg^-1 oxygen, 200 μg·kg^-1 hydrogen while measuring the linear polarization curve of the treated steel. The result showed that a two layered oxide scale with the Ni-rich outer layer and Cr-rich inner layer were form on the steel, which is similar to the oxide scale formed during PWR service; the amount of the deposited Pt on the pre-oxidized steel was from 4.37 to 7.37 μg·cm^-2 while the water containing Pt from 10 to 100 μg·kg^-1. With the increase of the Pt concentration of the treated solutions, E_corr decreased sharply while current density slightly changed, which revealed that the pre-oxidized steel samples with Pt deposit exhibit a better corrosion resistance.