During the operation of a 300MW subcritical boiler of a power plant, there is a low temperature of the SCR inlet flue gas under medium and low load conditions. In order to effectively solve the problem of low SCR inlet temperature under low load conditions, and improve the adaptability of the coal type. Three kinds of wide load denitration technology reform schemes are proposed. With the boiler thermal system simulation software BESS, the thermal calculations of the three transformation schemes were carried out. The results show that: the Scheme C is the optimal solution. After the transformation, the temperature of the SCR inlet flue gas increased by 21°C under the ultra-low load condition, and the exhaust gas temperature increased by about 7°C. At the same time, the possible impacts of the reform of the Scheme C and the key issues that need to be paid attention to during the transformation process are evaluated and discussed.