For a better understanding of slagging characteristics of Zhundong coal and solving its slagging problem, entrained flow reactor with multiple reaction segments was used to simulate air staging combustion condition in PC boiler. The slagging characteristics of Zhundong coal in various excess air ratio conditions was investigated, the morphology and melting characteristics and its burnout rate were analyzed using SEM-EDX and XRD. The results show that the burnout rate of Zhundong coal is more than 99％ at 1 250 ℃, and the influence of excess air ratio ranging from 0.7 to 1.0 on the char burnout is not obvious. With the excess air ratio increasing in the primary zone, the content of mullite increases, while the slagging characteristic reduces gradually. The Si, Fe, Na are enrich in slagging, while the content of Al is lower, and slagging is more serious. The aluminosilicate of iron is easy to form low temperature eutectic under lower excess air ratio, and it will cause slagging seriously. Therefore, the excess air ratio of the primary zone should be above 0.7 to avoid slagging seriously, and combustion mixed with low iron coal will reduce slagging of Zhundong coal.