Abstract: In order to control the high-temperature corrosion of water-wall, the pinning atmosphere was measured and the flake pieces were analyzed by SEM, EDS and XRD. The results show that the main reasons of water-wall high-temperature corrosion are cycle-by-cycle variation of reductive atmosphere. The area of most intense of reductive atmosphere and the concentration of H ₂S is between OFA and SOFA. The possibility of the high-temperature corrosion of this area is great. Dual tangential circle wall firing can raise the concentration of H ₂S at front-wall and back-wall. The outside corrosion product is Fe ₂O ₃, and on the contrary,the inside one is FeS. The alternation of the pinning atmospheres from oxidation atmosphere to reductive atmosphere which caused by load was a key factor of the high-temperature corrosion. In actual operation of boiler, optimizing air distribution mode and keeping the pinning atmosphere stabilization can reduce the rate of the high-temperature corrosion to low NO _x combustion boilers.