The reheat steam temperature of China's firstly built double-reheat boiler is sharply lower than the design value. To solve this problem

the quality of coal as fired and the heat absorption capacity of the boiler heating surface was analyzed. Moreover

the flue gas recirculation thermal control scheme was improved. On this basis

the comprehensive temperature improvement scheme was proposed

including optimizing the coal mill combination type

regulating the burner elevation angle

increasing the over fired air volume

improving the soot-blower'sputting-in-service mode and adjusting the flue gas recirculation amount. Furthermore

the condition test to explore the effect of burner's swinging angle and flue gas recirculation fan speed on temperature of the first reheat and second reheat steam were carried out. After debugging optimization

the reheat steam temperature of the boiler can reach 610~620 ℃ at high load and 590~590 ℃ at low and medium loads

which are similar with the design value

indicating the problem of low reheat steam temperature was solved well. The debugging experience has project reference value for subsequent similar units.