Abstract: Austenitic stainless steel, by virtue of its superior irradiation resistance, excellent corrosion resistance and good high-temperature strength, has become a critical structural material in nuclear reactors. Its irradiation damage behavior directly affects the macroscopic properties of the material and the operational safety of the reactor. Among these steels, 08Cr18Ni10Ti austenitic stainless steel is commonly used as the core baffle material for VVER. However, the evolution behavior of microstructural defects during the early irradiation stage (low-dose regime), especially the dynamic equilibrium state of vacancy-type defects, remains insufficiently understood. This study takes 08Cr18Ni10Ti austenitic stainless steel as the research object and focuses on the evolution of vacancy-type defects under different irradiation conditions. Irradiation was performed using 3.5 MeV Fe ions to systematically study the effects of temperature (room temperature and 350 ℃) and dose (0.2 dpa and 1.0 dpa) on the evolution of microscopic defects and crystal structure was systematically investigated. Prior to irradiation, the displacement damage and ion concentration distributions were calculated using the SRIM-2013 code in the Kinchin-Pease quick damage mode. SEM combined with energy-dispersive X-ray spectroscopy was employed to characterize the microstructure and precipitate distribution. After irradiation, lattice swelling was evaluated by grazing-incidence X-ray diffraction. The evolution of vacancy-type defects was traced via the S-parameter obtained from positron annihilation Doppler broadening spectroscopy, and variations in the types of vacancy-type defects were identified using S-W correlation curves. The S-parameter versus depth profiles were further fitted with the VEPFIT program using a two-layer model. Microstructural observations reveal the presence of fine spherical TiC particles and cubic TiN particles, with Ti(C,N) frequently surrounding the TiN cubes. The main results show that under room temperature irradiation, vacancy-type defects reach a dynamic equilibrium around 0.2 dpa, and further increasing the dose to 1.0 dpa causes no significant change. In contrast, under high-temperature (350 ℃) irradiation, vacancy-type defects continue to accumulate with increasing dose without showing a dynamic equilibrium, and no significant lattice swelling is observed. The study indicates that elevated temperature effectively raises the irradiation dose required for vacancy-type defects to achieve dynamic equilibrium and suppresses swelling by enhancing defect migration and recombination. This study clarifies the regulatory role of temperature in the attainment of dynamic equilibrium by vacancy-type defects, providing critical experimental evidence for a deeper understanding of the evolution mechanisms of vacancy-type defects, the refinement of irradiation damage prediction models, and the design of irradiation-resistant materials.