Abstract: Zhundong coal as a high quality steam coal has not been widely utilized due to its severe fouling and slagging problems during combustion. Understanding slagging and fouling mechanisms during coal combustion is crucial for the utilization of Zhundong coal. In this paper, the properties of ash deposits collected from various locations in 330 MW boilers with Zhundong Yihua coal as the primary fuel were investigated by ICP-OES, SEM-EDX, XRD and Ash Fusion Point Determination Meter. Results show that ash deposits from R-WW, R-PR FR, FS and PS are composed of loosely distributedsmall balls and clinker, while deposits from D-PS and R-PS are made up of large body structures. The ash deposits can be classified into silicates and sulfates based on morphological, elemental and mineral analysis. The deposits from D-PS and R-PS contain more silicates and they are found to have high viscosity and high AFT, while the deposits from R-WW, R-PR, FR, FS and PS contain more sulfates and they have low viscosity and low AFT.