Abstract: In chemical deoxygenation, using hydrazine serves as deoxygenation agentwhich has advantages, not only good results for removing oxygen can be obtained,but aiso it serves to passivate the piping and to reduce corrosion. In hightemperature and pressure test loop, effects of temperature and hydrazine concentrationon the deoxygenation are studied, test shows that at temperature of 90℃ andhydrazine be added 1. 5-3 times in excess of oxygen present in the system afterdeaeration, oxygen amount of 96-99% can be removed. At the initial start stage, oxygen amount of loop water is lower, safe operationcan be supported. Track test of dissolved oxygen affords useful information for study of corrosionof reactor material.