Autoreactive CD8+ T cell plays a key role in the pathogenesis of Type 1 diabetes (T1D), but the antigen spectrum that activate autoreactive CD8+ T cells is still not completely clear. Endoplasmic reticulum stress（ERS）has been implicated in the generation of β cell autoantigens and the enhanced immune visibility of β cells to autoreactive T cells. Here, we in-depth analyzed the major histocompatibility complex class I (MHC-I) associated immunopeptidome (MIP) of islets β cell under steady-state and ERS-state, and found couples of peptides exclusively present in the MIP of β cell line under ERS state. Among them, peptide OTUB258-66 derived from ubiquitin thioesterase OTUB2 showed immunodominance in NOD mice, and autoreactive CD8+ T cells targeting OTUB258-66 were diabetogenic in NOD mice. High glucose intake upregulated the expression of OTUB2 in the pancreas and amplified the OTUB258-66-specific CD8+ T cell response in NOD mice. Repeated administration with OTUB258-66 significantly reduced the incidence of T1D in NOD mice. This study not only provides an explanation for the role of ERS induced by environmental factors such as high glucose intake in promoting β cell autoimmune injury, but also provides a novel ERS-associated β cell autoantigens for developing specific immune intervention in prevention and treatment of T1D.