In order to study the variation of mechanical properties of cold-formed thin-walled steel materials under the coupling effect of high temperature and corrosion, a series of experiments involving neutral salt spray corrosion, high-temperature calcination, cooling and tensile tests were conducted. The mechanical properties of 180 S280GD+Z cold-rolled steel sheets with thickness of 1.5 mm, which underwent accelerated corrosion for 0-60 d and high temperature calcination from 20 to 800 ℃, were studied under cooling in air and cooling in water. The results indicate that under the coupling effect of corrosion and high temperature, the surface characteristics and failure modes of the steel are greatly affected by the cooling methods. When the corrosion rate is less than 6%, the corrosion has little impact on the mechanical properties of S280GD+Z steel. When the fire temperature is below 600 ℃, the fire temperature and cooling methods have insignificant effects on the yield strength and ultimate strength of S280GD+Z steel. However, under the coupling effect of corrosion and high temperature, when the fire temperature exceeds 600 ℃, the strength degradation of steel becomes the dominant factor affecting the strength of steel. The cooling method has a significant impact on the elongation of the steel. Under natural cooling conditions, the elongation increases and then decreases with the increase in fire temperature. Under immersion cooling conditions, the elongation shows an overall decreasing trend with the increase in fire temperature. A mathematical model was established to quantify relationship between the mechanical parameters of S280GD+Z steel and the corrosion rate and temperature under the coupling effect of corrosion and high temperature. Based on a simplified secondary plastic flow model, a constitutive model for S280GD+Z steel under the coupling effect of corrosion and high temperature was established.