Abstract: Oxide dispersion strengthened 316L (ODS-316L) steel is one of the candidate high-temperature structural materials for the generation Ⅳ nuclear reactors. The heat treatment process of ODS-316L steel will affect the nano-sized precipitates in the matrix. In this study, ODS-316L steel was fabricated with the mechanical alloying and spark plasma sintering processes, and annealed at two temperatures respectively. After the ODS-316L samples annealed at 1 100 ℃/1 h, part of the ultrafine grains grow into the micron-sized grains, hundred-nanometer sized Si—O precipitates appear at the grain boundaries of the micron-sized grains. While for the ODS-316L samples annealed at 1 150 ℃/1 h, the ultrafine grains almost grow into micron-sized grains. In addition to the coarsened Si—O precipitates, some hundred-nanometer sized precipitates of Y—Si—O and Ti—O also appear at the grain boundaries. The growth of ultrafine grains improves the plasticity of ODS-316L steel, while the precipitates coarsen at the grain boundaries or the trigeminal grain boundaries will give high damage to the tensile instability characteristics of ODS-316L steel.