Abstract： The cold bent 316L pipe was used to study the dependence of crack growth rate on dissolved oxygen in simulated temperature and pressure of primary side water environment. The crack growth rates were measured insitu realtime using the direct current potential drop method. Experimental results indicate that the crack growth rates increase with the increase of dissolved oxygen. When the oxygen content is less than 0.2 mg/L, the increase of the crack growth rate is very significant, while above this value, it becomes unconspicuous. This result was compared with those of other researchers’ and possible reasons were analyzed.