Abstract: With the continuous deepening of power market reform and the rapid development of new energy technologies, deep peak shaving of coal-fired power units has become the norm, and the difference between peak load and valley load of power grid day and night is large, and the frequency and depth of deep peak shaving are constantly strengthened, the risk of failure and leakage of metal parts, especially four tubes of boiler, is further increased. In this paper, a typical case of leakage failure of supercritical boiler envelope wall superheater caused by in-depth peak shaving is introduced, the problem of transverse fatigue crack is solved from the root, and the hidden trouble of four boiler tubes failure caused by alternating stress of metal material in the weak part of boiler heating surface tube caused by frequent and deep peak shaving is eliminated, it improves the safety and reliability of the unit and is worth popularizing and applying in the same type of thermal power unit.