Abstract: Ion irradiation experiments have been widely used in the evaluation of the radiation damage effect of the reactor pressure vessel（RPV） steels,which has a strict requirement for the surface state of the sample.The surface of RPV steel samples were treated by mechanical polishing,vibration polishing,electro-chemical polishing and vacuum annealing methods respectively.The damage states of the sample surface were characterized by slow beam positron annihilation Doppler broadening spectrum experiment.The stress states of the sample surface were characterized by nano-indentation test.The experimental results show that:for the RPV steel ion irradiated samples,it is recommended to use mechanical polishing and vacuum annealing treatment to deal with the sample surface,and then the electro-chemical polishing treatment method can be adopted.At the same time,the above conclusion is also applicable to the surface treatment of other low alloy steel ion irradiated samples,such as chemical composition,strength and toughness,and heat treatment.