Abstract: In view of the large-scale participation of thermal power units in deep peak shaving in recent years, the problems faced by low-load combustion of units. In this paper, taking a 350MW supercritical swirling combustion boiler in a power plant in Ningxia as an example, the steady combustion cold state test of boiler burner, burner heat load uniformity test, coal mill combination mode, oxygen content, air distribution mode and pulverized coal fineness adjustment are carried out. After the test, problems of unstable low load combustion, poor pulverized coal burnout, high NO_x concentration at denitration inlet and low steam temperature are significantly improved.