Molecular dynamics was used to simulate the dehydration process of kaolinte, and density functional theory was utilized to analyze the dehydration mechanism. The results show that significant changes of kaolinite are not found at 300600K, and in contradistinction to gradually increasing trend of coordination number of H atom, coordination number of Al atom is shown to decrease gradually after 700K, and it is showed in kaolinite XRD pattern that the relative content of alumina increases gradually, which indicates that the dehydration of kaonilite takes place in the process. The analysis on the dehydration mechanism reveals that the electronic transfer mainly occurs between 3p of Al and 2p of O in hydroxyl that is connected to the Al atom, and hybrid orbital is generated between 2p of O in the activated hydroxyl and 1s of H in the adjacent hydroxyl.