Abstract: The long-period corrosion behavior of 304L stainless steel was investigated by three long-period field hanging coupon immersion corrosion tests in the environment of a syngas ethylene glycol plant with temperatures of 116-128 ℃ and nitric acid mass fractions of 2%-20%. The results show that different degrees of intergranular corrosion and corrosion thinning occurred in 304L stainless steel after three long-period hanging coupon immersion corrosion under different conditions. The corrosion degree of stainless steel was the most serious under the condition of nitric acid mass fraction of 2%-8%, temperature of 116 ℃ and time of 156 d, and grain peeling occurred; the general corrosion rate was greater than 2 mm·a^-1, and the corrosion degree was serious corrosion. Pd in the catalyst of nitric acid reduction reactor was the main medium that rapidly accelerated the corrosion of 304L stainless steel. Pd and 304L stainless steel formed galvanic effect, thereby accelerating the corrosion of 304L stainless steel. 304L stainless steel was not recommended as the selection material for the de-heavy tower bottom area under the process condition.