Abstract: Biomass refers to the material derived directly from plants, thereby serving as a renewable, low-carbon emission, and environment-friendly energy source. Straw biomass is characterized by high alkali metal and ash content, where the ash caking easily occurs during combustion. This feature has become one of the most important factors limiting the use of industrial boiler fuel, particularly affecting the air distribution and complete combustion in the reaction chamber. In this study, a biomass combustion test device was designed with multi-layer secondary air, thereby explorg the influence on the NOx reduction rate and slagging in corn straw particle combustion. Two types of parameters were set firstly, including different primary and secondary air grading ratios, and the multi-layer ratios of secondary air. An evaluation was also made on the concentration of pollutants, such as CO and NOx in flue gas, combustion efficiency, and ash slagging rate. The results show that the concentration of NOx in flue gas significantly reduced, when the primary and secondary air were distributed in stages, whereas, the concentration of CO and NOx in flue gas changed in opposite directions, showing a competitive relationship. Specifically, a higher secondary air position or lower secondary air volume led to incomplete combustion of corn straw particles, and a significant increase in CO concentration. The temperature at each measuring point and the NOx concentration in the flue gas in the combustion chamber was reduced significantly, compared with the control group, under different secondary air distribution modes. Moreover, the emission of the lowest NOx concentration was released in W1 working condition, about 150 mg/m3. The NOx concentration was also significantly reduced, whereas, the slagging rate decreased greatly, with the lowest of 4.5%, when the secondary air was equipped with multi-layer air. The slagging rate of corn stalk increased significantly, with the increase of temperature T1, indicating that the temperature T1 was an important factor affecting the slagging of corn stalk particles during combustion. Correspondingly, the best working condition was achieved, where there was a relatively low NOx concentration and slagging rate under W1 working conditions. Furthermore, the incomplete combustion of corn stalk particles was attributed to the higher secondary air position or the lower secondary air volume, whereas, the CO concentration was attributed to the higher carbon content in ash. Additionally, the combustion efficiency decreased at the low temperature on the bottom of the combustion chamber. Consequently, four slagging indexes cannot correctly predict the change of slagging tendency under various fuel zone at temperature T1, such as acid-base ratio, alkalinity index Alc, Na content index, and silicon ratio index G. More importantly, when the temperature T1 was introduced into the silicon ratio index g, the modified Gt can be expected to well predict the slagging tendency of corn straw particles in the combustion zone.