Evolutions of defects and helium contained defects produced by atomic displacement and helium deposition with helium implantation at different temperatures in novel high silicon (NHS) steel are investigated by a slow positron beam.Differences of the defect information among samples implanted by helium to a fluence of 1 × 1017 ions/cm2 at room temperature,300℃,450℃ and 750℃ are discussed.It is found that the mobility of vacancies and vacancy clusters,a recombination of vacancy-type defects and the formation of the He-V complex lead to the occurrence of these differences.At high temperature irradiations,a change of the diffusion mechanism of He atoms/He bubbles might be one of the reasons for the change of the S-parameter.