Tumor vaccines are emerging as one of the most promising therapeutic strategies for cancer treatment. With the advantages of low toxicity, convenient production and stable quality control, peptide vaccines have been widely used in preclinical and clinical trials involving various malignancies. However, when used alone, they still suffer from significant challenges including poor stability and immunogenicity as well as the low delivery efficiency, leading to limited therapeutic success. Herein, the STING-activating peptide nanovaccine based on human serum albumin (HSA) and biodegradable MnO was constructed, which can improve the stability and immunogenicity of antigenic peptides as well as facilitate their uptake by dendritic cells (DCs). Meanwhile, Mn degraded from the nanovaccine can activate the STING pathway and further promote DCs maturation. In this way, the prepared nanovaccine can efficiently mediate T-cell immune responses, thereby exerting the effects of tumor prevention and therapy. Moreover, the prepared nanovaccine possesses the advantages of low cost, convenient preparation and good biocompatibility, showing great potential for practical applications.