Abstract: The precipitation dynamics of vanadium in HRB500 rebar after rolling deformation was investigated experimentally by stress relaxation method. The test results show that two turning points appear in the stress relaxation curves under constant temperature and strain after rolling,which correspond to the starting and finishing of precipitation of vanadium respectively. The precipitation-temperature-time （PTT）curves of vanadium present the C shape. With the increment of rolling deformation,the PTT curves move toward the left lower direction. When the rolling deformation is larger than 0.2,the fastest precipitation temperature of vanadium is about 870 ℃,and the precipitation can be finished within 3 sec. Finally,the precipitation particles were observed under TEM.