Abstract: With the increasing normalization of unit participation in flexible peaking,the importance of maintaining long-term safety and stability of equipment is becoming increasingly prominent. Based on the basic principles of coal-fired generator set boilers,the fatigue failure problem of water wall tube of ultra-supercritical power plant boiler is analyzed experimentally,the damage mechanism of water walls is revealed,the random characteristics of heat transfer deterioration in ultra-supercritical boilers are described and it is found that radial thermal stress has a positive correlation with temperature rise rate. It is pointed out that active control of hydrodynamic circulation is a good way to prevent heat transfer deterioration and thermal stress concentration and the suggestion that the operation adjustment of the wall temperature monitoring and maintenance of the water-cooled wall tube panel near the height of the phase change point should be emphasized is put forward,which provides reference for the safe operation of coal-fired power generation enterprises.