Abstract: In order to elucidate the problem of severe slagging and fouling during burning Zhundong coal,150 t/h boiler in Xinjiang Yihua company was used to carry out the assessment on all-Zhundong coal operation.The fouling configuration and morphology of water wall panel,super-heater,low temperature tube,and bottom ash were traced,and the slags from different positions were analyzed. The results show that the boiler suffers seriously slagging and fouling during entirely burning Zhundong coal.The slagging and fouling are caused by various forms of Na-bearing materials,such as sodium chloride and sodium oxides as well as elemental sodium released from coal and accumulated on the high temperature metal surface,reacting with SO_2、Fe_2O_3 to produce sulfates.The Fe-bearing minerals will decompose and combine with CaO,Al_2O_3 etc to produce low temperature eutectics.Such eutectics can decrease the ash melting temperature and accelerate the slagging and fouling propensity of Zhundong coal. Moreover,Ca and water in coal promote the accumulation of duster in the low temperature tube.