Abstract: Void swelling in austenitic stainless steel degrades the properties of materials used in reactors due to the accumulation behavior of radiation-introduced excess vacancies, which brings a serious threat to the safety of reactor. In this paper, electron beam irradiations were conducted by high voltage electron microscope in a temperatures range of 300~500 ℃, and insitu observation of the void evolution was carried out during irradiations. Void distributions were observed and void sizes were measured using transmission electron microscope after irradiations. The differences among the void evolution under different irradiation temperatures were investigated. The results show that large amounts of point defect clusters, loops, and voids can be observed under electron beam irradiations of different temperatures. Voids formed at 450 ℃and 500 ℃ are the largest, with a size of 13.3 nm and 14.5 nm, respectively. As the irradiation temperature increases, the diffusion of excess vacancies is enhanced, which leads to the enlargement of void size. These results are expected to provide a reference for forecasting the void swelling in austenitic stainless steel under different irradiation temperatures.