In this work, the inhibition effect of nitrate on the pitting corrosion of 17-4PH stainless steel was investigated in the chloride solution. Potentiodynamic and potentiostatic techniques were used to measure the pitting potential and induction time in various concentrations of chloride and nitrate ions. According to the results, the equation of was developed to show the relationship between the pitting potential and the concentrations of nitrate and chloride ions at room temperature. Moreover, it has been shown when the ratio of is greater than a threshold value of 0.35, the alloy remains passive in whole potentials during the potentiodynamic experiments. In addition, the results indicated that pitting is rarely observed in the potentials above the 400 mVSCE in the chloride solutions containing nitrate.