The main objective of this study was to investigate the reaction mechanism of zeolitization from coal fly ash by alkali hydrothermal treatment. The hydrothermal synthesis of zeolites was carried out using various alkali sources. The changes in the various properties, such as crystal structure, surface texture and cation exchange capacity, of the products and the amounts of Si4+ and Al3+ dissolved in the alkaline solution were investigated during the hydrothermal reaction. The mechanism of zeolite crystallization and the role of various alkali sources on the synthesis reaction were considered.