Abstract: In order to study the deep peak regulation capacity of a coal-fired power plant, the corresponding mathematical models of low load stable combustion, thermal-hydraulic circulation, wide-load denitrification, low-temperature corrosion of air preheater and auxiliary safety were established, and the calculation program was compiled based on Fortran language. In the low load stable combustion model, D-S evidence theory was used to judge the combustion stability of the boiler during deep peak regulation. The thermal-hydraulic circulation model used the nonlinear flow network system method to calculate key parameters of water cooling wall. In the wide-load denitrification model, the relationship between the inlet flue gas temperature of selective catalytic reduction reactor and the lowest operating temperature of catalyst was compared to determine whether the boiler denitrification was normally. The corrosion degree of air preheater was determined by comparing the relationship between acid dew point and the lowest wall temperature in the low-temperature corrosion model. The matching of the required pressure head and the characteristic curve of the fan was analyzed to judge the operation stability in the auxiliary safety model. Results show that the thermal-hydraulic circulation of 660 MW boiler in Shaanxi Qinling（Qinhua） Power Generation Co., Ltd. is safe under 20% boiler maximum continuous rating load, and the primary fan runs in the stable operating area. The program can be used in the engineering practice and provide guidance for the boiler deep peak regulation.