[en] The effects of reducing radiation level with primary circuit oxygenation operation during cold shutdown were described in this paper. Based on the results of radiological analysis of primary coolant, radiation measurement on workplace during the 1^st outage (without oxygenation operation) and the 2^nd, 3^rd and 4^th (with oxygenation operation) in Qinshan NPP, the effects of oxygenation operation on reduction of radiation level in working area were analyzed. It shows that oxygenation operation during cold shutdown process can reduce radioactive source term, radiation level in working area and collective dose effectively. It is one of the ways to carry out the ALARA