Abstract: To clarify the influence mechanism of Cl^-, Fe³⁺ and pH value on the corrosion behavior of S22053 stainless steel, five typical corrosive media were selected. Through three electrochemical test methods including polarization curve, Mott-Schottky curve and electrochemical impedance spectroscopy (EIS), combined with comparative analysis of ion concentration changes and existence states, the effects of various factors on the passive film performance and corrosion law of S22053 stainless steel were systematically explored. The results show that the increase of Cl^- concentration significantly increased the number of defects in the passive film of S22053 stainless steel, and this influence was more prominent in the outer passive film, directly leading to the decrease of passive film stability and the aggravation of corrosion process; relying on its strong oxidizing property, Fe³⁺ could not only promote the formation of passive film on S22053 stainless steel, but also participated in the cathodic reduction reaction, promoting the positive shift of both self-corrosion potential and semiconductor characteristic conversion potential. At the same time, it caused the increase of carrier concentration in the inner layer of the passive film, the decrease of carrier concentration in the outer layer, and the reduction of space charge layer thickness, ultimately aggravating the corrosion of stainless steel. Adding a small amount of HCl to the 6% (mass fraction) FeCl₃ solution to reduce the pH could effectively inhibit the hydrolysis reaction of Fe³⁺, increase the number of active Fe³⁺ in the solution, and then significantly aggravate the corrosion degree of S22053 stainless steel.