Abstract: In order to control the corrosion of system equipment and structural materials, the primary and secondary circuits of the nuclear power plant maintain weak alkaline reducing water chemistry conditions. Hydrazine is a bulk chemical reagent to be added to both the primary and secondary circuits. Because of its reducibility, it is mainly used for deoxidize, passivation, flushing, accident iodine removal, etc. In this paper, the main uses of hydrazine in nuclear power are summarized, and the primary deoxidize, AVT（R） deoxidize, secondary flushing and passivation, steam generator maintenance, and accident iodine removal are discussed respectively. Finally, some suggestions on the current application of hydrazine are given.