This study investigates effects of sintering temperatures on the hydration activity of the municipal solid waste incineration(MSWI) fly ash. MSWI fly ashes are rich in heavy metals, salts and toxic organic compounds. Therefore, in order to materialize it as cement materials, we should research the behavior of toxic materials at high temperature and the hydration activity of the MSWI fly ash sintered at high temperature. So, first of all, MSWI fly ashes were sintered at $800^{circ}C$, $1000^{circ}C$, $1100^{circ}C$, $1200^{circ}C$, $1300^{circ}C$, and $1400^{circ}C$ for an hour respectively. As a result of the first stage, MSWI fly ashes sintered at $1200^{circ}C$ and $1300^{circ}C$ contain cement components, $C_2S$(2CaO $SiO_2$) and $C_3S$(3CaO $SiO_2$) respectively. Moreover, the amount of heavy metals in MSWI fly ashes decreases as sintering temperature is raised. Secondly, the hydration activity of the MSWI fly ash sintered at various temperatures was measured. As a result of the second stage, MSWI fly ashes sintered at $1200^{circ}C$ and $1300^{circ}C$ have the great hydration activity. Finally, MSWI fly ashes sintered at $1300^{circ}C$ are the most suitable choice that could be recycled as cement materials.