Alkali and alkaline earth metals (AAEM), especially sodium, make a great contribution to the formation of fine particulates during coal combustion. Extraction and loading through chemical methods have been widely used for coal pretreatment to change the occurrence and content of sodium but could not load intrinsic minerals. In this study, synthetic char was used as a mineral carrier to study the characteristic of fine particulate formation during coal combustion. The silica and alumina were added to synthetic char as intrinsic minerals to study the interaction between sodium and Si and Al compounds in coal. The results show that the inorganic water-soluble sodium is more likely to form stable fine particles, while organic sodium prefers to react with silica and alumina in the absence of chlorine. Chemical reactions and physical capture are two main ways for sodium capture by silica and alumina. The content of sodium captured through chemical reactions is 2.4 times that by the physical way.