<p>In this work, the effect of heat flux on pitting corrosion behaviors and passive film properties of 304 stainless steel in 3.5 wt.% NaCl solution were investigated by the self-developed metal heat transfer surface testing system using electrochemical methods and surface analysis techniques. The results show that positive heat flux reduces the corrosion current density, inhibits the occurrence and growth of metastable and steady-state pitting corrosion, while the effect of negative heat flux is the opposite. The effects of heat flux on the semiconductor carrier concentration and the contents of Cr₂O₃ and NiO are not significant, but the effects on the contents of Fe (III) and Fe (II) in the outer layer of passive film are obvious. The positive heat flux increases the ratio of Fe (III) /Fe (II), thereby increasing the corrosion resistance of passive film, while the negative heat flux does the opposite.</p>