Abstract: Based on the principle of preheating combustion, the 90 t/h preheating combustion boiler for pulverized coal was designed and developed, as well as the experiment and performance test for this boiler with a high efficient combustion and low NO_x emissions were carried out. The results show that with the load ranging from 30% to 100%, the thermal efficiency of the boiler is higher than 92% and the NO_x emission is lower than 200 mg/m³, realizing high efficient and clean combustion under wide load conditions. As the boiler load decreases, the NO_x emission also drops, showing a good linear relationship. When the boiler load is 30%, the NO_x emission is only 78 mg /m³ also with the combustion efficiency of 97.91%, breaking through some technical bottleneck in difficult stable combustion and high NO_x emission under the condition of low load for conventional pulverized coal boiler. With the boiler load being 50%, the thermal efficiency reaches 93.9%, which is related to fuel preheating, preheated fuel combustion and burnout time. The two preheaters show a stable operation with the preheating temperature keeping 800~950 ℃, ensuring continuous and stable combustion of preheated fuel with wide load ranges. By adjusting air distribution, the mild combustion and ultra-low NO_x emission was achieved, with the NO_x emission of 47.89 mg/m³ when the boiler load is 70%. The successful demonstration project of 90 t/h pulverized coal preheating combustion boiler provides important support for the development and application of pulverized coal preheating combustion technology.