Abstract: During operation of supercritical circulating fluidized bed (CFB) boilers, high-temperature corrosion inevitably occurs on high-temperature heating surfaces. Under deep peak-shaving conditions, combustion instability leads to overheating of these surfaces, further exacerbating high-temperature corrosion of tube materials. To address corrosion issues induced by wall overheating on high-temperature heating surfaces in supercritical CFB units during deep peak-shaving, corrosive ash was prepared from wheat straw and coal. The ash was uniformly deposited onto specimen surfaces via a coating method. Corrosion behavior of three typical heat-resistant steels—T92, Super304H, and TP310HCbN were investigated under simulated flue gas conditions in a high-temperature tube furnace at three overheating temperatures (650, 700, and 750 ℃), aiming to elucidate the specific effects of co-firing wheat straw ash on the corrosion behavior of high-temperature heating surfaces. Analysis results of corrosion weight gain curves, corrosion product phases, and micro-morphology reveal that the corrosion products on high-temperature heating surfaces consist primarily of oxides of the base metal. Wheat straw contains elevated levels of Cl and K. Cl is identified as the key element inducing metal specimen corrosion, while K can promote the formation of additional low-melting-point eutectics in the co-fired ash, thereby accelerating corrosion. Consequently, increasing the wheat straw co-firing ratio promotes high-temperature heating surface corrosion. Temperature elevation significantly increased the initial corrosion rate and shortened the corrosion incubation period. As the temperature rises from 650 ℃ to 750 ℃, the inflection point of the corrosion rate advanced from 48−72 h to 24−48 h, accompanied by spallation of the corrosion layer, which resulted in a loose structure. Micro-morphological analysis indicated corrosion layer thicknesses of approximately 7 μm (T92), 9 μm (Super304H), and 4 μm (TP310HCbN) at 750 ℃. Cr content critically influenced the materials’ corrosion resistance. Cl was detected on the surfaces of T92 and Super304H via energy-dispersive X-ray spectroscopy (EDS). In contrast, TP310HCbN, possessing the highest Cr content, exhibited superior corrosion resistance and demonstrated enhanced stability under deep peak-shaving overheating conditions.