Zhundong coal has attracted an increasing concern due to its super huge reserve but high content of alkali metals. Oxy-fuel combustion of Zhundong coal benefits the near-zero emission of pollutants in coal-fired power plants and promotes the large-scale utilization of high-alkali coal. However, few efforts if any have been conducted on oxy-fuel combustion of Zhundong coal. The previous studies related to Zhundong coal were mainly focused on sodium behaviors but little work has been performed on calcium and iron, while calcium and iron are very likely to generate significant influences on fouling problems in combustion of Zhundong coal. The present study aimed to elucidate the release and transformation behaviors of sodium, calcium, and iron in oxy-fuel combustion of Zhundong coal using a fixed-bed reactor. Experimental results indicated that calcium in Zhundong coal was mainly present as the ammonium acetate-soluble form, while the iron existed in forms of hydrochloric acid-soluble and insoluble. With the increasing combustion temperature, the ash yields of Zhundong coals decreased and the volatilization ratio of sodium increased, while the temperature had a weak influence on ash yield and the release of water-soluble sodium between 800 and 1000 degrees C. The variations of total calcium with combustion temperature were not significant, but transformations among various chemical forms occurred. The decreased iron of the hydrochloric acid-soluble form was transformed into the insoluble form and discharged into gaseous phase. Compared to the air case, oxy-fuel combustion with 21% oxygen led to more sodium and iron retained in residual ash, while it promoted the release of calcium. The mineral transformation and ash formation were susceptible to the high content of carbon dioxide under oxy-fuel condition and were strongly associated with the chemical forms of sodium, calcium, and iron within Zhundong coals. The crystalline mineral species in Zhundong ash were obviously influenced by the combustion temperature and partly affected by the atmosphere. The differences of mineral species of Zhundong ash between air and oxy-fuel cases were mainly present in the range of 800-1000 degrees C, which was closely related to the decomposition of calcite and transformation of calcium. The oxygen content dependency of transformation behaviors of sodium, calcium, and iron was greatly different during oxy-fuel combustion. This work possibly offered an improved understanding of the functional mechanisms of sodium, calcium, and iron on fouling issues.